Sir Keir Starmer is facing his first by-election test since becoming Prime Minister after ex-Labour MP Mike Amesbury was jailed for punching a constituent in the street.
The 55-year-old was ordered to serve 10 weeks in prison after admitting to drunkenly attacking a man in Frodsham, Cheshire, last October.
Following his sentencing today, Amesbury was told to resign from the House of Commons in order to trigger a by-election in his Runcorn and Helsby constituency.
Reform UK demanded he quit immediately rather than wait for voters to kick him out of Parliament via a recall petition, which is likely to follow his custodial sentence.
Nigel Farage’s party are eyeing a by-election breakthrough in Runcorn and Helsby after coming second to Amesbury in the seat at last July’s general election.
Amesbury, who has been an MP since 2017, won the constituency with a 14,696-vote majority last summer as part of Labour’s landslide victory.
But Sir Keir’s bumpy start to life as PM means Labour are set to face a much tougher battle as they seek to hold on to the constituency at a likely by-election.
The Tories came third at July’s general election, more than 900 votes behind Reform.
Mike Amesbury, pictured arriving at his sentencing hearing, was ordered to serve 10 weeks in prison after admitting to drunkenly attacking a man in Frodsham, Cheshire, last October

It means Sir Keir Starmer is now facing his first by-election test since becoming Prime Minister, with a contest likely to be held in Runcorn and Helsby

Nigel Farage’s Reform UK are eyeing a by-election breakthrough in Runcorn and Helsby after coming second to Amesbury in the seat at last July’s general election
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Amesbury has been sitting as an independent MP in the House of Commons since being suspended by Labour following his arrest last year.
He claimed he was ‘threatened’ before the attack in his Cheshire constituency in the early hours of October 26.
But CCTV footage, exclusively obtained by MailOnline, at the time showed him throwing a punch seemingly without physical provocation.
Amesbury then continuing to hit the man multiple times while he lay on the ground.
The politician was filmed striking constituent Paul Fellows after the pair had a heated discussion by a taxi rank at 2am in Amesbury’s home town.
He then punched Mr Fellows, 45, five times as he lay on the floor in what a court heard was an unprovoked assault.
As Amesbury was handed a 10-week jail sentence at HMP Altcourse and ordered to pay a £280 fine, Judge Tan Ikram said: ‘Your reference to being a Member of Parliament brings negative impact for the office you are privileged to hold.
‘Your position means you ought to be a role model to others, that’s something you ought to be mindful of in everything you do.’
Amesbury is facing mounting pressure from all sides of the political spectrum to do the ‘honourable thing’ and resign his seat in the wake of the shocking incident.
Labour said residents in Runcorn and Helsby ‘deserved better’.

Amesbury pleaded guilty to a charge of common assault at an earlier hearing on January 17. Here he is pictured (right) outside Chester Magistrates Court today
Footage of the incident on October 26 last year provoked outrage after it was exclusively revealed by The Mail two days later.
It shows him lashing out and continuing to hit Mr Fellows until onlookers held him back.
The Mail obtained the CCTV after Amesbury went to police to report being ‘involved in an incident’ after he ‘felt threatened on the street’.
Speaking at the time, Sir Keir described the footage as ‘shocking’. He insisted the Labour Party had moved ‘swiftly’ to suspend Amesbury.
Amesbury pleaded guilty to a charge of common assault at an earlier hearing on January 17.
Sentencing at Chester Magistrates’ Court today, District Judge Ikram condemned ‘early hours drunken brawling’.
He said the risk of offending by Amesbury has been deemed low – but if he were to reoffend, the ‘risk of harm’ was deemed ‘medium’.
The judge went on: ‘If you punch someone in the head, he goes to the floor, you go on to punch him further and it’s only because of by-standers it stops, the court must consider the risk of harm’.
Richard Derby, defending, told of the ‘threats’ experienced by Amesbury as an MP and told how he had been advised to install panic alarms’.
But the judge said: ‘Security threats are there for many people who work in the public service at the moment.’
Mr Derby added that Amesbury was already carrying a ‘second sentence’ in terms of mental and emotional element, as well as the ‘shame’ which will ‘stay with him forever’.
Mr Derby said Amesbury had offered his resignation to the Labour Party before it announced he would not be readmitted.
He also said Amesbury’s six members of staff face uncertainty.
After Mr Derby argued against community service, Judge Tanweer replied: ‘Are you suggesting I should treat him differently to anyone else who punches someone to the floor in the early hours?’

The 55-year-old was filmed on CCTV punching constituent Paul Fellows after the pair had a heated discussion by a taxi rank at 2am in Amesbury’s home town of Frodsham, Cheshire

Amesbury, who has sat as an independent MP after being kicked out by Labour, then punched Mr Fellows, 45, five times as he lay on the floor

Footage of the incident on October 26 last year provoked outrage. It showed Amesbury lashing out and continuing to hit Mr Fellows (pictured) until onlookers held him back
Amesbury, who spoke only to confirm his name, address and date of birth, sat in the glass-fronted dock in a dark suit, white shirt and red tie, stared forward during the hearing.
Alison Storey, senior specialist prosecutor with the Crown Prosecution Service, said: ‘This was a persistent assault by Mike Amesbury which continued while the victim was on the floor, offering no aggression.
‘The victim was alone and not part of a group and CCTV footage showed that he was not being threatening or aggressive towards Mike Amesbury.
‘After the initial punch which knocked the victim to the ground, Mike Amesbury struck the victim at least a further five times while he was on the floor.
‘The CPS will always seek to prosecute violent offences in accordance with our legal test regardless of who the perpetrator is.’
Jade Marsden, the Tory candidate who stood against Amesbury last year, today called for him to resign ‘out of respect for his constituents that he has so badly let down’.
She said: ‘An MP should set an example to their constituents and wider society.
‘When MPs take part in initiatives like the one punch (manslaughter) campaigns, they do it for a reason and that’s to raise awareness that one stupid moment, losing control can lead to death.
‘He’s no longer in a position do that and should go out of respect for his constituents that he has so badly let down.’
Amesbury was previously warned he could have faced jail at an earlier court hearing last month, after which Labour sources said he would not have the whip restored.
Under Parliamentary rules, he is likely to face a recall petition – once all appeals are exhausted – due to his jail sentence.
This would give local voters the chance to kick him out of the House of Commons.
A by-election would be triggered if 10 per cent of eligible registered voters sign the recall petition.
Being jailed for more than 12 months would have automatically disqualified him from being an MP.
Amesbury will be allowed to stand as a candidate in a by-election triggered by a successful recall petition.
Reform UK chairman Zia Yusuf said today: ‘The great people of Runcorn deserve far better than waiting six weeks for a recall petition to take place.
‘We call on Mike Amesbury to do the honourable thing and resign.’
A Labour Party spokesperson said: ‘The Labour Party took swift action following Mike Amesbury’s completely unacceptable actions and he is no longer a Labour MP or a member of the Labour Party.
‘It is right that Mr Amesbury pleaded guilty and has now been sentenced.
‘Local residents in the Runcorn and Helsby constituency deserved better and we look forward to them getting the representation they deserve in the future with a new Labour MP.’
Peter Stanyon, chief executive of the Association of Electoral Administrators (AEA), said: ‘An MP being convicted of an offence and receiving a custodial sentence (including suspended) automatically triggers a recall petition.
‘A petition is open for six weeks, and if at least 10 per cent of voters in the constituency sign it, the MP loses their seat and a by-election is triggered.
‘However, a recall petition only opens when the Speaker of the House of Commons notifies a petition officer. This would not be expected until after the appeal period, and when any appeals have been heard.
‘We send our best to the Halton Borough Council petition officer and elections team as the lead authority, and their colleagues at Cheshire West and Chester Council who administer a cross-boundary section of the constituency, as they wait to find out more.
‘In our new blueprint report into electoral reform, we recommend abolishing recall petitions and instead legislating for an MP’s automatic disqualification from office based on the three recall triggers in the Recall of MPs Act 2015.
‘We also believe that if petitions remain in place, they should end as soon as the threshold of 10 per cent of registered electors signing is reached, rather than remaining open for six weeks.’

Sir Keir is pictured here with Amesbury on the campaign trail in Weaver Vale, Cheshire, in 2019

Amesbury was previously warned he could have faced jail at an earlier court hearing last month, after which Labour sources said he would not have the whip restored
Leaving court after the hearing in January, Amesbury, who has been an MP for eight years and a Labour member since he was 17, said of his conduct: ‘It’s highly regrettable and of course I’m sincerely sorry to Mr Fellows.’
Chester Magistrates’ Court heard both men had been drinking and met by chance before discussing the closure of a local bridge.
However, the MP then snapped and flattened Mr Fellows, before yelling: ‘Don’t threaten your MP. You won’t threaten your MP again, will you, you f****** soft lad.’
Ms Storey, prosecuting, said Mr Fellows ‘wasn’t aggressive’, adding: ‘There was engagement… over several minutes. There were no raised voices.’
Mr Derby, defending, accepted there was ‘no provocation’, but said the assault was a ‘momentary incident’.
District Judge Ikram had warned Amesbury: ‘Guidelines suggest a sentence starting with a high-level community order up to a prison sentence. I’m leaving all options open.’
As he was jailed, Judge Ikram told him: ‘I accept this is a one-off incident in an otherwise unblemished career. There may well be an impact on your future career.
‘You’ve served this country in high office but the court treats all who come before it as equals. The focus of the court is public protection.
‘I’m of the view that unprovoked drunken behaviour in the street is too serious to be dealt with by way of community service or a community order.’
Mr Derby lodged an immediate request for bail pending an appeal but he was refused.
Amesbury looked ashen-faced but said nothing as he was led to the cells by two dock officers.
In a statement at the time, the MP called the incident ‘deeply regrettable’.
Approached at his home in Frodsham yesterday, Mr Fellows declined to comment ahead of Amesbury’s sentencing.
The pair had been rowing in the taxi queue over Labour’s plans to means test the winter fuel payment and the closure of the county’s Sutton Weaver swing bridge moments before the fracas.
The bridge, which sits on a main road into the town from the nearby M56, was set to be closed for 33 days in January and March for vital engineering works.
Mr Amesbury has previously called the closure ‘unacceptable’.
Both men had spent the previous evening drinking and the argument turned violent when Mr Amesbury lashed out with a left hook.
An eyewitness present on the night said Amesbury told her that Mr Fellows had been ‘constantly on at him’ before he ‘snapped’ – although footage showed he was stood at a distance and was neither gesturing nor pointing towards the MP.
She said: ‘I had a quiet word with him afterwards and said, ‘mate, what have you done… You’ve messed up. everything’.
‘He replied, ‘No I haven’t, he was on at me constantly and wouldn’t leave me alone. What was I supposed to do? Was I not supposed to snap?’
‘I told him that he was an MP and in the public eye and no matter what was said he couldn’t go around lamping people.’
The woman said Mr Amesbury was ‘steaming drunk’.
‘He had a brief sober moment when he realised what he’d done and he just looked down and said ‘s***’,’ she added.
She claimed Mr Fellows seemed ‘intent’ on provoking the MP.
But Hugo Deynham, a Tory councillor on Chester West and Cheshire Council, which covers Frodsham, told the Mail ‘single punches kill people’ and such acts of violence should be condemned in the strongest terms.
‘From what you can see on the video it looks pretty brutal, there is no condoning it,’ Mr Deynham said.
‘We need to send a message that single punches do kill people and the full force of the law must come down on those guilty of such offences.’
Amesbury had attended a police meeting about community safety earlier on the Friday evening before drinking in Kash 22 and The Cholmondeley Arms.
The incident took place in the early hours of the Saturday morning after the pub closed at around 2.15am.
Amesbury has previously demanded tougher sentences for violent crime. During riots which followed the Southport murders last summer, he posted on X that ‘thugs and criminals’ should get a decade in jail.
In 2020, he spoke during a Westminster Hall debate on the assault of retail workers, saying: ‘Anyone who is assaulted deserves to be protected by the law… What is more, despite ample evidence, some cases are not being prosecuted, even when there is clear video footage of an assault.’
Amesbury has been involved in the Labour Party for nearly 40 years.
Born in the Wythenshawe area of Manchester, Amesbury revealed he joined Labour aged 17 when his family were living in Castleford, West Yorkshire – with the 1984-5 miners’ strike being a key part of his motivation.
Graduating from the University of Bradford with a degree in community studies, Ames bury worked as a careers advisor and became a councillor in his native Manchester in 2006.
He was later elected to the party’s policy-making arm, the National Policy Forum (NPF), as well as serving as an adviser to Tameside Council, a director of a housing trust in Manchester and a director of the city’s arts festival.
He worked as a careers adviser and was a senior parliamentary adviser to Angela Rayner when she was shadow education secretary.
And the politician also became an adviser and stakeholder manager for Andy Burnham during his successful campaign to be Manchester mayor in 2017.
In his maiden Commons speech after being elected Weaver Vale MP in 2017, he said his father was a carpet fitter and then a publican, while his mother cleaned caravans and served school dinners – and revealed he was the first in his family to get a degree.
Amesbury told MPs: ‘As a lad born in Wythenshawe, Manchester, I never envisaged that I would have the honour of sitting on these green benches’.
He was initially seen as a rising star, with Sir Keir appointing him Labour spokesman for work, pensions and employment from July 2018 and then spokesman for housing and planning in April 2020.
That year, he introduced a private members’ bill to give schools guidance on uniform costs in 2020, which became law a year later and enforced from September 2022.
In 2018, his cockapoo dog, Corbyn, won a prize when MPs held a bring-your-dog-to-work day. The pet won the ‘people’s vote’ accolade for best dog in an online vote open to the public.
After his dog was presented with the prize, he revealed his son came up with his name, adding: ‘I always find it entertaining when my wife shouts ‘Corbyn’ when he runs off the lead.’
But in 2022, the Manchester United and rugby league fan stepped back to focus on his constituency work.
Mr Amesbury, who is married with a teenage son and lives at a £685,000 home, briefly returned to the shadow Cabinet in the levelling-up brief.
But Amesbury has had troubles. In 2014, writing in a local newspaper, he revealed having suffered depression and been prescribed anti-depressants.
In March 2019, Mr Amesbury was forced to apologise for sharing an anti-Semitic caricature on Facebook in 2013 in a post referencing an ‘Illuminati’ conspiracy theory. He claimed at the time that he had not shared the post intentionally.
Meanwhile, in 2023 a man was given a restraining order after being found guilty of stalking and harassing him – leaving Amesbury feeling ‘that little bit more anxious’.
The last MP to be jailed was Fiona Onasanya in January 2019.
The Labour politician was given three-month sentence for perverting the course of after lying over a speeding ticket.
The Peterborough MP was the first sitting MP to be jailed in 28 years – and was removed from office in May that year after a recall petition.
MPs convicted of criminal offences have previously remained in parliament.
In one example, former Labour MP Claudia Webbe was convicted of harassment against a woman in 2021 and given a 10-week suspended sentence, later reduced to community service on appeal.
She remained as an independent MP until losing her Leicester East seat to the Conservatives last year.