If 54 MPs submit letters of no confidence in the prime minister a vote on his leadership would then be held. However, not all of these MPs have publicly said they have submitted a letter.

Equally, there are likely to be other MPs who who have sent letters to Sir Graham Brady, who organises Tory leadership contests, but who have not made them public.

Here is the full list of those that have broken cover to urge him to step down.

Tim Loughton

Constituency: East Worthing and Shoreham

Majority: 7,474

First elected: 1997

Mr Loughton served as a junior minister for children under David Cameron. He supported leaving the EU in the 2016 referendum and backed Boris Johnson over Jeremy Hunt in the 2019 leadership election. Not known if he has submitted a no-confidence letter.

David Davis

Constituency: Haltemprice and Howden

Majority: 20,329

First elected: 1987

A prominent supporter of Brexit, David Davis served as Secretary of State for Exiting the EU under Theresa May but resigned after deciding he couldn't support her plans for a deal. He also came second to David Cameron in the 2005 Conservative leadership election. Not known if he has submitted a no-confidence letter.

Andrew Mitchell

Constituency: Sutton Coldfield

Majority: 19,272

First elected: 1987 (he lost his seat in 1997 but was returned to parliament in 2001)

A former cabinet minister under David Cameron. Andrew Mitchell supported remaining in the EU in 2016 and has been a key critic of Boris Johnson's cuts to international development funding. Not known if he has submitted a no-confidence letter.

Roger Gale

Constituency: North Thanet

Majority: 17,189

First elected: 1983

A consistent critic of Boris Johnson, Roger Gale voted against the government's plans to break international law during the EU Trade deal negotiations in 2020. Has submitted a no-confidence letter.

Peter Aldous

Constituency: Waveney

Majority: 18,002

First elected: 2010

Peter Aldous has criticised the government over its handling of universal credit and argued they should have kept the £20 top-up to the payment that was introduced during the pandemic. Has submitted a no-confidence letter.

Anthony Mangnall

Constituency: Totnes

Majority: 12,724

First elected: 2019

Before becoming a MP, Anthony Mangnall was an adviser to former Foreign Secretary William Hague. In Parliament, he has rebelled against the government on votes on Covid restrictions and international aid cuts. Has submitted a no-confidence letter.

Sir Gary Streeter

Constituency: South West Devon

Majority: 21,430

First elected: 1992

A supporter of Remain in the 2016 EU referendum. He did not support Boris Johnson in the 2019 leadership contest. Has submitted a no-confidence letter.

Tobias Ellwood

Constituency: Bournemouth East

Majority: 8,806

First elected: 2005

A junior minister under David Cameron and Theresa May, Tobias Ellwood is a former soldier and now serves as chairman of the defence select committee. He supported remaining in the EU in 2016. Has submitted a no-confidence letter.

Aaron Bell

Constituency: Newcastle-under-Lyme

Majority: 7,446

First elected: 2019

Mr Bell rebelled against the government when it ordered MPs to vote to change standards rules when Owen Paterson was found to have broken them. Has submitted a no-confidence letter.

Nick Gibb

Constituency: Bognor Regis and Littlehampton

Majority: 22,503

First elected: 1997

Previously served as schools minister under David Cameron, Theresa May and Boris Johnson. He supported staying in the EU in 2016 and backed Michael Gove for the party leadership in 2019. Has submitted a no-confidence letter.

Craig Whittaker

Constituency: Calder Valley

Majority: 5,774

First elected: 2010

Mr Whittaker supported Remain in 2016 and has rebelled against Boris Johnson's government twice over Covid restrictions. Not known if he has submitted a no-confidence letter.

Neil Hudson

Constituency: Penrith and The Border

Majority: 18,519

First elected: 2019

Dr Hudson has rebelled against the government several times, including by voting against their plans to cut foreign aid and raise National Insurance. Not known if he has submitted a no-confidence letter.

Caroline Nokes

Constituency: Romsey and Southampton North

Majority: 10,872

First elected: 2010

Ms Nokes attended cabinet as immigration minister under Theresa May. She left government under Boris Johnson and was one of the 21 Conservative MPs who had the whip removed in 2019 for voting against the government's Brexit position. She currently serves as chair of the Women and Equalities Select Committee. Has submitted a no-confidence letter.

Mark Harper

Constituency: Forest of Dean

Majority: 15,869

First elected: 2005

Chief Whip under David Cameron. During the Covid-19 pandemic Mr Harper has repeatedly criticised the government's policies, speaking out against lockdowns and calling for looser legal restrictions. Has submitted a no-confidence letter.

William Wragg

Constituency: Hazel Grove

Majority: 4,423

First elected: 2015

A consistent rebel against the government, Mr Wragg has voted against their proposals 20 times during the current parliament. He also chairs the Commons Public Administration and Constitutional Affairs Select Committee. Has submitted a no-confidence letter.

Steve Baker

Constituency: Wycombe

Majority: 4,214

First elected: 2010

A prominent backbench supporter of leaving the EU. Mr Baker previously submitted a letter of no confidence in Theresa May and backed Boris Johnson when she stood down as prime minister. Not known if he has submitted a no-confidence letter in Mr Johnson.

Julian Sturdy

Constituency: York Outer

Majority: 9,985

First elected: 2010

Mr Sturdy is a backbench MP who has voted against the government several times, including by rebelling against Covid restrictions. Not known if he has submitted a no-confidence letter.

John Baron

Constituency: Basildon and Billericay

Majority: 20,412

First elected: 2001

A supporter of leaving the EU in 2016, Mr Baron is also notable for repeatedly criticising UK military intervention abroad. Not known if he has submitted a no-confidence letter.

Stephen Hammond

Constituency: Wimbledon

Majority: 628

First elected: 2005

Stephen Hammond was a supporter of remaining in the EU in 2016 and was one of the 21 Conservative MPs who had the whip removed in 2019 for voting against the government's Brexit position. Has submitted a no-confidence letter.

David Simmonds

Constituency: Ruislip, Northwood and Pinner

Majority: 16,394

First elected: 2019

Mr Simmonds previously called on Dominic Cummings to resign when he was accused of breaching lockdown rules in May 2020. Not known if he has submitted a no-confidence letter.

Alicia Kearns

Constituency: Rutland and Melton

Majority: 26,924

First elected: 2019

Ms Kearns sits on the executive of the influential backbench 1922 committee and was the leading figure in the "Pork Pie plot" to oust the PM. She has also been critical of the government's position on the rights of transgender people. Has submitted a no-confidence letter.

Sir Bob Neill

Constituency: Bromley and Chislehurst

Majority: 10,891

First elected: 2006

Sir Bob supported remaining in the EU in 2016 and currently chairs the Commons Justice Select Committee. Has submitted a no-confidence letter.

Steve Brine

Constituency: Winchester

Majority: 985

First elected: 2010

Mr Brine was one of the 21 Conservative MPs who had the whip removed in 2019 for voting against the government's Brexit position and has rebelled against the government on votes on Covid restrictions several times. Has submitted a no-confidence letter.

Anne Marie Morris

Constituency: Newton Abbot

Majority: 17,501

First elected: 2010

Ms Morris previously had the Conservative whip withdrawn for voting in favour of a Labour motion to extend the provision of free school meals during school holidays until Easter 2021. Has submitted a no-confidence letter.

Jeremy Wright

Constituency: Kenilworth and Southam

Majority: 20,353

First elected: 2005

Now a backbencher, Jeremy Wright previously served as Attorney General and then Culture Secretary under David Cameron and Theresa May. Not known if he has submitted a no-confidence letter.

Elliot Colburn

Constituency: Carshalton and Wallington

Majority: 629

First elected: 2019

Mr Colburn has disagreed with the government on transgender rights and criticised the decision to exclude trans people from its proposed conversion therapy ban. Has submitted a no-confidence letter.

Andrew Bridgen

Constituency: North West Leicestershire

Majority: 20,400

First elected: 2010

Mr Bridgen supported leaving the EU in 2016 and Boris Johnson in the 2019 leadership election. He has previously submitted letters of no confidence in both David Cameron and Theresa May. Has submitted a no-confidence letter.

John Stevenson

Constituency: Carlisle

Majority: 8,319

First elected: 2010

Mr Stevenson supported remaining in the EU in 2016. He has criticised the government over universal credit and called on them to maintain the £20 top-up implemented during the pandemic. Has submitted a no-confidence letter.