He was sentenced to 10 weeks behind bars after he pleaded guilty to the assault by beating of 45-year-old Paul Fellows in Frodsham, Cheshire, in the early hours of 26 October.
He announced his resignation as MP for Runcorn and Helsby in a social media post on Monday, describing the assault as a “deeply regrettable incident” for which he had “rightly been punished”.
“I am sincerely sorry to Paul Fellows, my family, colleagues and constituents,” he added.
A by-election will now be triggered in Runcorn and Helsby, where constituents will vote to elect a new MP.
Image: Mike Amesbury leaving Chester Crown Court in February. Pic: PA
By-election a ‘big test’ for PM
It will be the first by-election since Sir Keir Starmer became prime minister, in what Sky News’ political correspondent Liz Bates said would be a “big test” in a seat where Reform UK came second last year.
“Losing it would be an unmitigated disaster given the 14,000 majority achieved last time round,” said Bates.
Amesbury came first in Runcorn and Helsby with 22,358 votes at the 2024 general election – equating to 52.9% of the electorate.
Reform UK came in second with 7,662 votes (18.1%) and the Tories in third with 6,756 votes (16%).
Reform has yet to announce a candidate, but Karen Shore, the deputy leader of Cheshire West and Chester Council, will run for Labour.
The Conservatives have opted for Sean Houlston, a membership services manager for the National Federation of Builders.
Image: Sir Keir Starmer’s government has been polling very badly indeed. Pic: PA
When will the by-election be?
Under parliamentary procedure, an MP cannot simply resign but must be disqualified from holding their seat.
To do this, they must apply for a role in the paid office of the Crown, meaning they automatically lose their seat because working for the Crown is not seen as impartial.
Titles include the crown steward and bailiff of the Chiltern Hundreds and the Crown Steward and Bailiff of the Manor of Northstead.
Rachel Reeves has now appointed Amesbury to be steward and bailiff of the Three Hundreds of Chiltern, meaning the parliamentary seat is officially vacant.
Once he does, the chief whip will put forward a motion to Lindsay Hoyle, the Commons speaker, to officially begin the process of disqualifying the MP – known as “moving the writ”.
The Speaker then puts the motion to MPs for a vote. If they agree, the writ passes through the Commons and ends up with the returning officer in the local constituency who oversees the by-election.
The writ is typically issued within three months of the MP resigning from their seat and in doing so, the date of the by-election is fixed.
It could potentially coincide with the local elections in May.
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Gaza and transatlantic trade are set to dominate talks between Donald Trump and Sir Keir Starmer when the pair meet in Scotland on Monday.
Downing Street said the prime minister would discuss “what more can be done to secure the ceasefire [in the Middle East] urgently”, during the meeting at the president’s Turnberry golf course in Ayrshire.
Talks in Qatar over a ceasefire ended on Thursday after the US and Israel withdrew their negotiating teams.
Mr Trump blamed Hamas for the collapse of negotiations as he left the US for Scotland, saying the militant group “didn’t want to make a deal… they want to die”.
Sir Keir has tried to forge close personal ties with the president, frequently praising his actions on the world stage despite clear foreign policy differences between the US and UK.
The two leaders are expected to discuss this agreement when they meet, with the prime minister likely to press the president for a lowering of outstanding tariffs on imports such as steel.
Prior to the visit, the White House said the talks would allow them to “refine the historic US-UK trade deal”.
Extracting promises from the president on the Middle East may be harder though.
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1:30
Should aid be dropped into Gaza?
Despite some reports that Mr Trump is growing frustrated with Israel, there is a clear difference in tone between the US and its Western allies.
As he did over the Ukraine war, Sir Keir will have to walk a diplomatic line between the UK’s European allies and the White House.
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Trump: ‘It doesn’t matter what Macron says’
The UK, French and German leaders spoke over the weekend and agreed to work together on the “next phase” in Gaza that would see transitional governance and security arrangements put in place, alongside the large-scale delivery of aid.
Under pressure from members of his own party and cabinet to follow France and signal formal recognition of Palestine, Sir Keir has gradually become more critical of Israel in recent months.
On Friday, the prime minister said “the starvation and denial of humanitarian aid to the Palestinian people, the increasing violence from extremist settler groups, and Israel’s disproportionate military escalation in Gaza are all indefensible”.
Government sources say UK recognition is a matter of “when, not if”, however, it’s thought Downing Street wants to ensure any announcement is made at a time when it can have the greatest diplomatic impact.
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1:19
Baby Zainab starved to death in Gaza
Cabinet ministers will be convened in the coming days, during the summer recess, to discuss the situation in Gaza.
The UK has also been working with Jordan to air drop supplies, after Israel said it would allow foreign countries to provide aid to the territory.
Downing Street says Ukraine will also likely be discussed in the meeting with both men reflecting on what can be done to force Russia back to the negotiating table.
After the meeting at Turnberry, the prime minister will travel with the president to Aberdeen for a private engagement.
Mr Trump is also expected to meet Scottish First Minister John Swinney while in the country.