Boris Johnson is resigning as an MP after accusing a Commons investigation into whether he misled Parliament over partygate of attempting to “drive me out”.

The former prime minister, in a statement to the media, compared the Privileges Committee probe to a “kangaroo court” as he announced his intention to step down as MP for Uxbridge and South Ruislip.

He said, after receiving a letter from the Conservative-majority committee, he believed it was “determined to use the proceedings against me to drive me out of Parliament”.

“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,” he said.

The announcement, coming only hours after his resignation honours list had been published, means the Conservatives are likely to face a tough battle to hold onto the London seat at a by-election.

It was the second by-election triggered on Friday following former culture secretary Nadine Dorries’ decision to quit the Commons immediately, rather than wait until the next election.

The Privileges Committee has been investigating whether Mr Johnson misled MPs when he assured them that Covid rules were followed in No 10 following allegations of lockdown-busting parties.

In a scathing attack, he accused the committee of producing a yet-to-be-published report “riddled with inaccuracies and reeks of prejudice” while providing him with “no formal ability to challenge anything they say”.

He said the panel of MPs had “still not produced a shred of evidence that I knowingly or recklessly misled the Commons”.

But he said he thought their “purpose from the beginning has been to find me guilty, regardless of the facts”.

“They know that I corrected the record as soon as possible; and they know that I and every other senior official and minister – including the current Prime Minister and then occupant of the same building, Rishi Sunak – believed that we were working lawfully together,” he said.

“I did not lie, and I believe that in their hearts the committee know it.”

He continued: “So I have today written to my association in Uxbridge and South Ruislip to say that I am stepping down forthwith and triggering an immediate by-election.

“I am very sorry to leave my wonderful constituency. It has been a huge honour to serve them, both as mayor and MP.”

He has called on the inquiry being led by veteran Labour MP Ms Harman into his partygate comments — a probe he argued was a “witch hunt” and “revenge for Brexit” — to cease.

Mr Johnson returned to Parliament in 2015, having previously represented Henley in the Commons between 2001 and 2008 and serving two terms as mayor of London.

He was promoted to foreign secretary by Theresa May when she took over from David Cameron, but he later resigned over her Brexit policy.

The 58-year-old succeeded her as prime minister in 2019 and would go on to secure a landslide victory at that year’s snap winter general election.

He announced his resignation from No 10 in July 2022 after he lost the support of his party over his handling of sexual assault allegations against former deputy chief whip Chris Pincher.

In his statement on Friday, in which he appeared to leave the door open for a return to Westminster, Mr Johnson was critical of Mr Sunak’s administration, questioning the decision to increase taxes and abandoning the prospect of a free trade deal with the US.

Mr Johnson held his Uxbridge seat with a majority of 7,200 votes at the 2019 contest, with Labour his closest rival.

The by-election is likely to be tricky for Mr Sunak’s party, with Labour more than 10 points ahead of the Tories in most opinion polls.

Polling released by Savanta suggested Sir Keir Starmer’s outfit currently holds a 14-point lead over the Tories in Mr Johnson’s former west London constituency.

Richard Mills, chairman of the Uxbridge and South Ruislip Conservative Association, said Mr Johnson had been an “outstanding” advocate for the community “contrary to external perception”.

He said the local party respected “his decision to stand down” in response to what Mr Mills called a “co-ordinated campaign against him” by the Privileges Committee.

Mhairi Black, SNP deputy Westminster leader, said the former No 10 incumbent “jumped before he was pushed”.

Deputy Labour leader Angela Rayner said the British public was “sick to the back teeth of this never ending Tory soap opera played out at their expense” as she urged voters to “turn the page with a fresh start” under a Labour government.

Liberal Democrat deputy leader Daisy Cooper said it was “good riddance” to Mr Johnson.