Boris Johnson has resigned as the MP for Uxbridge & South Ruislip with immediate effect after receiving a letter from the privileges committee about its Partygate probe.
Johnson, 58, released a 1,000-word resignation statement stressing he was "bewildered and appalled" by the privileges committee's drive to oust him from the House of Commons.
The ex-Prime Minister said: "It is very sad to be leaving Parliament - at least for now - but above all I am bewildered and appalled that I can be forced out, anti-democratically, by a committee chaired and managed, by Harriet Harman, with such egregious bias.
"I am being forced out by a tiny handful of people, with no evidence to back up their assertions, and without approval even of Conservative party members let alone the wider electorate.
Boris Johnson is said to have rewarded those who have been supportive of himPA"I believe that a dangerous and unsettling precedent is being set."
In a swipe against Sunak, Johnson added: "When I left office last year the government was only a handful of points behind in the polls. That gap has now massively widened.
"Just a few years after winning the biggest majority in almost half a century, that majority is now clearly at risk.
"Our party needs urgently to recapture its sense of momentum and its belief in what this country can do.
"We need to show how we are making the most of Brexit and we need in the next months to be setting out a pro-growth and pro-investment agenda."
Rishi Sunak has been warned Boris Johnson's resignation is "dangerous"ReutersThe former Prime Minister, who was first elected as the MP for the West London seat in 2015, also took aim at former senior civil servant Sue Gray.
Gray led Whitehall's investigation into Partygate and is soon expected to join Labour leader Sir Keir Starmer at Southside.
Johnson claimed he no longer believes "that it is any coincidence" that Gray will become the Leader of the Opposition's chief of staff.
He added: "Nor do I believe that it is any coincidence that her supposedly impartial chief counsel, Daniel Stilitz KC, turned out to be a strong Labour supporter who repeatedly tweeted personal attacks on me and the Government."
The 58-year old, who played a leading role in the campaign for the United Kingdom to leave the European Union, alleged that the privileges committee's "witch-hunt" was taking "revenge for Brexit and ultimately [trying] to reverse the 2016 referendum result".
Boris Johnson leaves his home in LondonPAJohnson was facing an investigation from the privileges committee over whether he "knowingly or recklessly" lied to MPs about parties held in Whitehall while Covid-curbing restrictions were in place.
The former Prime Minister sat down for a grilling from the cross-party committee in March.
The committee has not yet responded to Johnson's statement and its report has not yet been released.
Johnson, who was twice-elected as Mayor of London, previously served as Henley MP from 2001 to 2008.
His decision to quit the Commons forces a by-election in Uxbridge & South Ruislip.
Nadine Dorries is a fervent supporter of ex-Prime Minister Boris JohnsonPAJohnson ally Nadine Dorries triggered a separate contest in Mid Bedfordshire earlier today as she quit ahead of the release of Johnson's resignation honours.
The former Prime Minister was returned to the House of Commons in 2019 with a 7,210-vote majority in Uxbridge & South Ruislip.
However, Labour's double-digit lead in the opinion polls now means Sir Keir could snatch the Tory seat from Sunak's hands.
A sitting Prime Minister has never lost their seat in an electoral contest.
However, ex-Prime Minister Arthur Balfour was defeated by his Liberal Party challenger in Manchester East in 1906 just months after he left Downing Street.
Gordon Brown's seat of Kirkcaldy & Cowdenbeath was a notable casualty after the former Labour leader stood down in 2015, with the Scottish National Party hoovering up votes north of the border.
