Crossing the political divide immediately before PMQs, Mr Wakeford told Boris Johnson that "you and the Conservative Party as a whole have shown themselves incapable of offering the leadership and government this country deserves".

Part of the 2019 intake of Tory MPs who won former Labour seats, Mr Wakeford said the country needed a government that "upholds the highest standards of integrity and probity".

Follow live partygate updates as high-profile Tory calls for PM to go

Conservatives 'a party trying to defend the indefensible'

Mr Wakeford, whose majority in Bury South is just 402 votes, said the Conservatives were "a party trying to defend the indefensible".

"There's been far too many issues where I've felt we've been on the wrong side," he told broadcasters later on Wednesday.

"And compromise isn't a dirty word, but it is possible to compromise too far. And when it's getting to a point where it's difficult to explain some of these issues, then you know it's wrong."

The new Labour MP continued: "This isn't a matter of just deciding this morning, you know, I want to be a Labour MP - this has been many months in the build up.

"And whether it goes back to the issues over free school meals and Dominic Cummings, or over Universal Credit and the cost-of-living crisis... the Owen Paterson affair or now 'partygate', there has been a lot of... build up to this and a lot of soul searching that's taken many sleepless nights."

He added: "This is something that has taken many months to come to, and it's not been an easy decision, if anything it's been the most difficult decision I have ever had to make. But I do think it's the right decision for me, I think it's the right decision for Bury South."

Sir Keir Starmer welcomes MP's defection

Labour leader Sir Keir Starmer welcomed Mr Wakeford's defection, saying: "He has always put the people of Bury South first."

Labour shadow ministers Angela Rayner and Yvette Cooper both told Sky News they welcomed Mr Wakeford's defection.

MP in talks with Labour since October

Mr Wakeford has been in talks with Labour since October, and it was called "Operation Domino", a party source told Sky News correspondent Joe Pike.

A Conservative MP told Sky News the Tory chief whip "hauled" Mr Wakeford in last night "and it sent him over the edge when they threatened his seat" with having its boundary changed.

"This is what bully tactics look like," the MP said.

Mr Wakeford submitted a letter of no confidence in Mr Johnson, but as he is no longer a Tory MP, it does not count.

Read more: All the Tory MPs who have submitted a vote of no confidence in the PM

PMQs kicks off moments after MP defects

The former Tory announced his defection moments before Mr Johnson faced MPs at Prime Minister's Questions.

Sir Keir kicked off PMQs by welcoming Mr Wakeford to the Labour Party and said he was happy to welcome any other MPs who wanted to defect.

Mr Wakeford was seen on the Labour benches wearing a Union flag facemask.

The PM did address his defection, telling MPs the Conservatives won Bury South for the first time in generations under him and pledged - to very loud jeers from Labour and cheers from Tory MPs: "We will win again at the next election under this prime minister."

Mr Wakeford's defection comes a day after the Mr Johnson said "nobody told me" attending a Downing Street garden party during the May 2020 lockdown was breaking COVID rules.

During PMQs, the prime minister faced calls for his resignation from senior Conservative MP David Davis and Sir Keir over "partygate"., but the PM kept telling them they needed to wait for the investigation by top civil servant Sue Gray to finish.

Mr Davis told the Commons: "I expect my leaders to shoulder the responsibility for the actions they take. Yesterday he did the opposite of that.

"So, I will remind him of a quotation which may be familiar to his ear: Leopold Amery to Neville Chamberlain. You have sat too long here for any good you have been doing. In the name of God, go."

Mr Johnson said the report was coming "next week".

Parts of Labour Party angry at Wakeford's defection

Not everyone in the Labour is happy with Mr Wakeford's defection, with Momentum, the left-wing arm of the party, saying he should be "nowhere near the Labour Party" and that a by-election should be held in Bury South.

In 2020, Mr Wakeford co-sponsored and voted for a private members bill that would "enable the recall of Members of the House of Commons who voluntarily change their political party affiliation; and for connected purposes".

Young Labour - members aged 14-26 - also voiced their upset at Mr Wakeford being admitted.