Video report by ITV News Political Correspondent Libby Wiener
Jeremy Corbyn has stood by his shadow health minister, insisting the pair are "cool" and dismissing the leaked criticism of him as "banter".
Meanwhile Jonathan Ashworth dismissed the comments in which he criticised the Labour leader as "just winding up an old mate" and also described them as "banter".
In the leaked recording, published by the Guido Fawkes website, the shadow health secretary said the situation facing Labour was “abysmal” because voters “can’t stand Corbyn” and think the party has “blocked Brexit”.
Adding that a Labour majority at the election was "not going to happen".
He also said he thought the civil service machine would “pretty quickly move to safeguard security” if Mr Corbyn entered Number 10.
And Mr Ashworth also said party MPs “f****d it up” in 2016 in their attempt to remove the Labour leader, saying they “went too early”.
Soon after the explosive recordings emerged, the shadow health secretary was approached by ITV News and insisted: "I was just winding up an old friend...I was pulling his leg."
Mr Ashworth claimed the comments were made when he was "joking around" with a Tory friend, later saying he was not sure they were friends anymore.
Mr Ashworth went on to say the recording was proving to be a "desperate distraction from the Tories", as they "don't want to be held to account on their record of mismanaging and pushing the NHS into the ground".
In a follow-up interview with ITV News Political Correspondent Carl Dinnen he backtracked on the leaked comments and said "Labour are going to win this election".
Mr Ashworth added: "I was having a banterish conversation with an old friend, turns out he's not a friend, cause he's leaked it, trying to...lull him into a false sense of security cause he's a Tory activist.
"But the reason this has come out is because the Tories are running away from their record on the NHS...this is more dirty tricks from the desperate Tory party."
Speaking on Tuesday afternoon, Mr Corbyn said he had spoken to Mr Ashworth "straight away" before adding the Labour candidate "has my full support" and "I'm cool with Jon".
He added the shadow health secretary's comments were just an example of his "rather odd sense of humour".
"He said to me it was all about reverse psychology banter as in football supporters and the other person was saying the opposite about their party and it all got a bit out of hand."
ITV News Political Correspondent Libby Wiener explains the latest slow down to Labour's campaign
However, Boris Johnson seized on the comments and said they were proof Labour was losing votes over its Brexit stance.
He said Britain could be led by Jeremy Corbyn on Friday morning, who he labelled a "Hamas-backing, IRA-supporting, anti-Semitism-condoning appeaser of the Kremlin".
In a speech at JCB Cab Manufacturing Centre's headquarters in Staffordhsire, the Prime Minister said: "If you doubt me, look at what his health spokesman said today, Jon Ashworth.
"He revealed that he thought his own leader is a security risk.
"And there is another fact Mr Ashworth mentioned which I think is even more terrifying when you look at the year ahead and the prospects for our country.
"Jon Ashworth made it absolutely clear that the reason Mr Corbyn is failing to persuade some people to vote for him is he is blocking Brexit - he won't get Brexit done.
"Don't just listen to me, look at what his health spokesman Jon Ashworth has said.
"He is absolutely right."