Labour voters should support Boris Johnson in the general election, former Labour MP Ian Austin has said.
The former minister, who resigned from the party in February, said Jeremy Corbyn was “completely unfit to lead our country”.
Speaking to the BBC, Mr Austin said: “I can’t believe it has come to this.”
Asked about his comments, Labour’s Rebecca Long Bailey said telling people to vote Conservative was “absurd”.
She said Mr Austin had done “great work” as an MP but added that it was “no secret” that he had differences with the Labour leader.
Chief Secretary to the Treasury Rishi Sunak called Mr Austin’s comments a “truly devastating indictment of Jeremy Corbyn’s leadership”.
Speaking to the Express and Star, Mr Austin said “I must do everything I can to stop Jeremy Corbyn from getting into power.”
The BBC’s political correspondent Chris Mason says the interview was “astonishing”.
“We should be clear he has had a long standing run-in with Mr Corbyn,” he says.
“We know that he doesn’t like the Labour leader but still, on day two of a general campaign, for someone who has been Labour MP for much of his time in Westminster to say ‘vote Conservative’ is incredible.”
Mr Austin became a Labour councillor in Dudley in his twenties, later working as a press officer for Gordon Brown.
He was elected MP for Dudley North in 2005 and served in Mr Brown’s government from 2008-2010.
Mr Austin quit the party earlier this year blaming Mr Corbyn for “creating a culture of extremism and intolerance”.
His comments comes as Tom Watson announced he was stepping down from his role as deputy party leader and as an MP.
He said the decision was “personal, not political” and that he would continue to campaign for the party.