The Labour leader has come under intense pressure to say whether he would back Leave or Remain in the Final Say vote which he has promised within six months if Labour wins the 12 December general election.
Labour says it will decide its position at a special conference in the spring, but Mr Corbyn's announcement that he will not personally take sides will heighten expectations that MPs will be allowed to campaign either for or against the “credible” Brexit deal which their leader says he will negotiate with Brussels.
Asked which side he would campaign on, Mr Corbyn said: “I will adopt, as prime minister at the time, a neutral stance, so I can credibly carry out the result of that to bring our communities and country together.”
Adopting a neutral stance would bring to a stop the “endless debate about the EU and Brexit”, he said.
But he was jeered by sections of the audience as he insisted he would be able to negotiate a credible Brexit deal.
Mr Johnson said that Corbyn’s position “seems to have mutated”.
“He now says he’s going to be neutral on the deal that he proposes to do,” said the prime minister. “I don’t see how he can do a deal when he wants to be neutral.”
Mr Johnson returned repeatedly during his 30-minute grilling to his well-worn argument that Britain must “get Brexit done” in order to move on. But he faced boos as he claimed that the failure to deliver Brexit was to blame for a loss of trust in politics.
And there was laughter from the studio audience when the prime minister said it was “absolutely vital” to tell the truth in the election.
Mr Johnson faced hostile questioning over past newspaper columns which have been denounced as Islamophobic and homophobic and was forced to deny being personally responsible for the growth of “racist rhetoric” in society.
Defending notorious comments about “tank-topped bum boys” and Muslim women looking like “letterboxes”, the prime minister said: “I defend my right to speak out.”
Mr Johnson has been dogged by the articles he wrote as a journalist, including the recent revelation that he wrote that seeing “a bunch of black kids” scared him.
He denied the phrases were offensive – claiming they could only be “made to seem offensive” if taken out of context.
“If you go through all my articles with a fine-toothed comb and pick out individual phrases, there’s no doubt that you can take out things that can be made to seem offensive,” he told the BBC Question Time audience.
Mr Corbyn faced tough questioning during the two-hour broadcast over his own record on handling antisemitism in his party.
One audience member said he was “terrified” to see footage of Corbyn shake the hand of an activist who had heckled Jewish MP Ruth Smeeth out of a meeting, and told him “I don’t buy this whole ‘nice old grandpa’. I see that video and that tells me all I need to know.”
Mr Corbyn accepted that Ms Smeeth and others had suffered “unbelieveable” levels of abuse, but added: “Bad behaviour, misogyny, racism in any form is absolutely not acceptable in any form whatsoever in my party or in society.”
Mr Johnson was loudly barracked as he defended his decision – which he said he had taken “ages ago” – not to have a parliamentary report on alleged Russian interference in UK politics published before the election.
He appeared to suggest critics of the decision, such as the Intelligence and Security Committee chairman Dominic Grieve, were conspiracy theorists, as he said: “This is complete Bermuda Triangle stuff”.
Reports suggest that the investigation looked into alleged links between wealthy Russian nationals and the Conservative party and claims of interference in the 2016 EU referendum.
Mr Johnson said: “There is absolutely no evidence at all to show any influence into any British electoral event.
“And the reason I won’t (publish) – or at least the reason I decided not to ages ago – is that I see no reason to interfere with the normal timetable just because there is an election going on.”
Also given a rough ride by questioners on the special general election broadcast was Liberal Democrat leader Jo Swinson, who apologised for her role in supporting the increase in university tuition fees in the coalition government and admitted her party “didn’t get everything right” on austerity while in government.
After entering the election on a pitch that she could become prime minister, Ms Swinson acknowledged that it would be “a strange thing” if she ended up in Downing Street.
She made clear the Lib Dems were now presenting themselves not as a potential government but as the best means for preventing a majority Tory administration.
Declaring herself “dismayed” at the choice between Johnson and Corbyn for prime minister, she said: “It’s the Liberal Democrats who are able to win seats from Boris Johnson and the Tories. It’s not the case that Jeremy Corbyn and he Labour Party are going to be able to win seats from the Conservatives..
“That’s why voting Liberal Democrat is the way to deprive Boris Johnson of a majority.”
Rejecting suggestions that she was splitting the pro-referendum vote by standing against Labour, she said “my conscience wouldn’t be clear” if she did not ensure the electorate had a chance to vote to stop Brexit, warning: “This might be the last chance.”
Asked if she would form another Lib Den-Tory coalition, Ms Swinson said “certainly not under Boris Johnson”, describing the Tories as “off the charts” under his leadership.
Mr Corbyn again rejected the prime minister’s charge that he would usher in a second independence referendum in Scotland, saying he would not allow it for “two years at least” after taking power.
But Scottish first minister Nicolas Sturgeon said she believed that Mr Corbyn would drop his resistance to an “IndyRef2” if he needed SNP support for a minority administration in a hung parliament.
“Having heard Jeremy Corbyn, do you think he is going to walk away from the chance to end austerity, to protect the NHS, to stop Universal Credit, simply because he wants for a couple of years to prevent Scotland having the right to self-determination?” she asked.
“Jeremy Corbyn supports the right to self-determination for every other country in the world. I’m not sure he is going to compromise the chance of a Labour government for that issue.”
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