Len McCluskey is the General Secretary of Unite the Union, one of the Labour Party's major donors. Mr McCluskey told Sky News he would be supporting Rebecca Long-Bailey in the Labour leadership contest. Following the announcement Mr McCluskey was grilled on why he had chosen to support a close ally of Jeremy Corbyn.
Mr McCluskey was asked: "Why are you placing so much hope in Rebecca-Long Bailey?"
He replied: "Well my view is that the reason we lost the general election by such a massive margin was because of Brexit.
"It wasn’t because of the policies in the manifesto, although quite evidently there were far too many policies.
"There was not sufficient focus on the policy issues and Rebecca has accepted that.
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Len McCluskey is the General Secretary of Unite the Union
Rebecca Long-Bailey is a close ally to Jeremy Corbyn
"It was Brexit which actually lost us the election.
"Some of us including me were pointing out to our leadership that it was going to happen.
"The more we slid into being perceived as a Remain party we would pay consequences in our heartlands.
"Unfortunately we were proven right even worse than what I was expecting."
Last week Jeremy Corbyn was savagely called a "bone-headed Marxist throwback to 1981" by political commentator John Rentoul during an interview on talkRADIO.
TalkRADIO host Mike Graham and Mr Rentoul were discussing Labour leadership candidate Rebecca Long-Bailey during the interview.
Mr Rentoul said: "Rebecca Long-Bailey is completely different from Jeremy Corbyn."
The talkRADIO host replied: "She has told me in the past that she thinks he is right about everything.
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The 2019 general election result
"What she will do is have his same domestic policies that were in the Labour manifesto."
Mr Rentoul said: "In a way that is not as bad, I don’t agree with them.
"This sort of religious faith in nationalising the railways is just utterly bizarre but it is not the same as being obsessed with Venezuela.
"She is not some kind of bone-headed Marxist throwback to 1981 in the way that Jeremy Corbyn is.
"She is much more of a mainstream naive leftie and you need a bit of that in the Labour Party mix."