On the recording, former Guardian journalist Seumas Milne, who has been described as on the “far Left” of the Labour Party, can be heard talking to Mr Corbyn about how to find a “form of words” to “shut down” the outrage over the Labour leader’s refusal to use Trident to defend Britain.
Mr Milne told Mr Corbyn: “We need, without looking defensive, to seal down the Trident thing so it doesn’t keep intruding in the next few days. We just need a form of words to shut down the nuclear question.”
It followed a humiliating performance by the Labour leader on the Meet the Leaders Question Time on Friday.
He provoked widespread fury by refusing to say whether he would press the nuclear button if Britain needed it after a series of questions from the audience and David Dimbleby.
Spin doctor Seumas Milne, left, with Jeremy Corbyn
We need, without looking defensive, to seal down the Trident thing so it doesn’t keep intruding in the next few days
Mr Milne, who went to the top public school Winchester College, is the son of former BBC director general Alasdair Milne.
Labour former minister Tom Harris claimed that Mr Corbyn chose Mr Milne “because of his political views” not because of his skills as a communicator.
He pointed out that like Mr Corbyn he is “a hate figure” for people on the moderate wing of the party.
Mr Milne was reportedly on the 10.20pm train from York to King’s Cross drinking a small bottle of wine on his way home after the debate when the conversation was recorded.
Jeremy Corbyn was heckled over his refusal to use Trident
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The discussion was, according to reports, punctuated with laughter, as they poked fun at the idea of a “second strike” in the event of a nuclear attack.
The conversation was recorded by a fellow passenger.
According to reports there were long silences as Mr Milne listened to the Labour leader.
The conversation appeared to highlight how Mr Corbyn’s vague pledge to “do whatever is necessary to protect our people” is a cynical attempt to hide the truth that he would never use nuclear weapons, not even as a last resort.
Mr Milne congratulated Mr Corbyn for his woeful performance in the debate, saying: “You got through it.”
Addressing the nuclear issue Mr Milne said: “The whole discussion is completely surreal.
“No one has used nuclear weapons for 72 years and they are not independent at all. The idea Britain would independently retaliate for some nuclear attack is all completely off the wall.”
After Mr Corbyn agreed with him, Mr Milne continued: “Completely bonkers. That’s why I’m always saying we should just say we will do whatever is necessary to protect our people.”
Mr Milne congratulated Mr Corbyn for his woeful performance in the debate
Mr Milne also agreed with Mr Corbyn that Mr Dimbleby “pushed nuclear a lot”.
He then laughed as they discussed how a Corbyn government would never use nuclear weapons if Britain had already been attacked.
Mr Milne said: “The truth is, nobody would. It’s a complete emperor’s new clothes.
“If there has been a first strike, what is the point of the second strike?”
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The televised debate saw Jeremy Corbyn, Amber Rudd, Paul Nuttall, Caroline Lucas, Angus Robertson, Tim Farron and Leanne Wood go toe-to-toe
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The politicians taking part in the debate
After Mr Corbyn spoke, Mr Milne added: “Yeah, it would have already failed and there would be no point.
“The whole discussion is completely bonkers.”
The frank exchange came following Mr Corbyn’s shaky TV performance on Friday, when his peacenik views and refusal to say whether he would press the nuclear button came under scrutiny.
Mr Corbyn, who is still not sure if he is still vice president of the Campaign for Nuclear Disarmament or not, looked extremely uncomfortable as the audience ridiculed him over his avoidance of the question, even refusing to say he would launch weapons if Britain was at risk from a country like North Korea.
Mr Corbyn regused to say whether he would press the nuclear button
He was specifically tackled on whether he would use the weapons as a “second strike” if Britain was hit by a nuclear strike first.
Mr Corbyn said: “Any circumstances where anyone is prepared to use a nuclear weapon is disastrous for the whole planet.
“That is why there has to be a process of disarmament.
“The reality is we have to protect ourselves. We would not use it as first use and if we would use it millions are going to die. I would decide on the circumstances at the time.”
The show descended into farce when Mr Dimbleby asked the Labour leader if he wanted to respond to a point by a man in the audience on the need for having nuclear weapons.
“No,” he said crossly, shaking his head.