The broadcaster, who is often regarded as the voice of the nation after decades of fronting Question Time, election night specials and state occasions, strayed into unfamiliar territory by backing a longstanding complaint by Corbyn's supporters.
The Labour leader will join the leaders of the Liberal Democrats, UKIP, the Green Party and Plaid Cymru, and the SNP's leader at Westminster, at the BBC event, which has been boycotted by the Prime Minister.
Fresh from the hot lights of the TV studio, Theresa May will be back on the road as we continue the last full week of campaigning before the General Election as the Conservative battlebus takes the PM to the West Midlands.
The not-a-debate between Jeremy Corbyn and Theresa May is the political story making the headlines in Tuesday's papers, with the i calling the clash between the party leaders and Jeremy Paxman "bruising".
"What one's bound to say is that if I was sitting in Brussels and I was looking at you as the person I had to negotiate with, I'd think, "She's a blowhard who collapses at the first sign of gunfire"," he said.More news: Captain and coach will not always be on same page: Gavaskar
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Corbyn replied: "All of our manifesto is fully costed".
Her assessment garnered more than 9,000 retweets.
She said: "It's a staggering cost; would you like to know how much your policy is going to cost, Mr Corbyn?"
Mr Corbyn, a lifelong opponent of nuclear weapons who has made clear that he would never authorise their use, nevertheless indicated he would issue the customary final instructions to the commanders of the Trident submarine fleet if he became prime minister.
Mrs May also repeated her "no deal is better than a bad deal" slogan when asked if she was prepared to walk away from Brexit talks.
"We won't start the negotiations with megaphone diplomacy, threatening Europe with some kind of offshore tax haven on the shores of Europe", he said in a dig at May's efforts to handle Brexit. "Come on Prime Minister, come and have a chat, come and have a debate and I can be ever so polite, but there are a number of questions I want to put to you". In negotiations you have to recognise that you're not in there to get a deal at any price.