Mr Mann criticised the Conservative leader for her handling of Brexit negotiations and claimed her days were numbered before the programme’s host questioned whether Mr Mann had any faith in his own party’s front man.
Mr Dimbleby went on to roast the Labour political after he told the host he had failed to research the subject properly and tried to deny having criticised Mr Corbyn’s leadership ability.
He said: “You’re not that much better with Jeremy Corby are you? – Because you’re always saying he’s too old or he won’t make it through.”
In an attempt to distance himself from the comments the Bassetlaw MP told Mr Dimbleby not to “believe everything that you read” in the media.
He added: “You should be better prepared than that.”
However, the BBC host quickly proved that Mr Mann had accused Mr Corbyn of being too old to govern.
He said: “I’m reading from the what you said on the 27th January to the Jewish Labour movement conference.
“You said ‘the next election by 2022 by which stage Jeremy Corbyn will be 73 and facing the prospect of being Prime Minister at 78 so I don’t think he’ll be doing it’.”
The Labour MP looked embarrassed as the quotes were read back to him, proving the had criticised his leader’s suitability to run the country.
Mr Dimbleby added: “I hope your blushing.”
In a desperate attempt to prove he was right the politician suddenly jumped to life to challenge Me Dimbleby for having got the dates wrong.
Flustered, he said “It wasn’t in January it was in September, it was the third of September and it was in response to a question.”
His attempt to restore his credibility after being shown up by Mr Dimbeby was met with an outburst laughter from other panellists and the audience.
Despite the comments made by Mr Mann, if Labour won an election in 2022, Mr Corbyn would not be the oldest person to enter Downing Street.
William Ewart Gladstone was appointed Prime Minister at the age of 82 when he was appointed to the position in 1892.