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Here is a timeline of the recent political crises that have engulfed the prime minister’s leadership.

April 2 2022

David Warburton, the MP for Somerton and Frome, had the Conservative whip withdrawn after allegations of sexual harassment and cocaine use emerged.

April 11 2022

Imran Ahmad Khan, the then-Tory MP for Wakefield, was found guilty of sexually assaulting a 15-year-old boy in 2008.

Khan, who maintains his innocence, was expelled from the Conservativeparty and resigned, triggering a by-election that Labour won in June. Khan was jailed for 18 months in May.

April 12 2022

Boris Johnson and Rishi Sunak were fined for attending the prime minister’s birthday bash in Downing Street in June 2020, as part of a Metropolitan police probe into alleged parties at the heart of the government during the pandemic.

Johnson offered a “full apology” as opposition parties characterised him as the first prime minister to have been found to be in breach of the law.

April 21 2022

Johnson faced the prospect of a parliamentary investigation after MPs agreed to refer him over claims he lied to parliament about Downing Street parties during lockdowns.

May 4 2022

Neil Parish quit his seat in Tiverton and Honiton after admitting watching pornography in the Commons.

Tiverton and Honiton was snatched by the Liberal Democrats in a June byelection, overturning a Conservative majority of more than 24,000.

May 17 2022

An unnamed Conservative MP was arrested on suspicion of rape and sexual assault offences spanning seven years. Tory chief whip Chris Heaton-Harris urged the MP to stay away from parliament but did not suspend the whip.

May 25 2022

Sue Gray published her full report into lockdown-busting parties in No 10 and Whitehall, detailing events at which officials drank so much they were sick, sang karaoke, became involved in altercations and abused security and cleaning staff at a time when millions of people across the country were unable to see friends and family.

June 6 2022

The government’s anti-corruption tsar resigned from his post and called on the prime minister to do the same, accusing him of breaking the ministerial code.

John Penrose, Conservative MP for Weston-super-Mare, said Johnson had failed to address the Sue Gray report’s “very serious criticisms” of the leadership at 10 Downing Street.

June 6 2022

Johnson’s authority was damaged by a confidence vote which saw 41% of his MPs try to oust him. He insisted he had secured a “decisive” victory as Tory MPs voted by 211 to 148 in support of him, but the scale of the revolt left him wounded.

June 15 2022

Lord Geidt resigned as ethics adviser a day after telling MPs it was “reasonable” to suggest the prime minister broke the ministerial code by breaching lockdown laws.

June 24 2022

Defeat in two crunch by-elections and the subsequent surprise resignation of the Conservative party co-chairman pitched Johnson’s leadership into a fresh crisis.

Cabinet minister Oliver Dowden said he and Tory supporters were “distressed and disappointed by recent events” and told the prime minister that “someone must take responsibility”.

June 30 2022

Chris Pincher resigned as deputy chief whip after allegedly assaulting two fellow guests the evening before at the Carlton Club.

Downing Street said Johnson was not aware of any “specific allegations” about Pincher when he appointed him to the whips office, but it emerged over the following days that he was told about allegations against him as far back as 2019.