Ian Hernon made his remarks in the wake of Labour's decision to pay substantial damages to seven whistleblowers who were involved in an investigation by BBC's Panorama. All were former party employees who worked with journalist John Ware, who was also awarded damages. The case was settled last month, with Labour offering an unreserved apology and agreeing to pay damages for what it acknowledged were "defamatory and false allegations" made in a Labour press release issued in response to the documentary, in which it accused the seven of "having acted in bad faith".
Mr Corbyn responded to the decision by saying he was disappointed with the party's decision which he described as being politically rather than legally motivated.
Len McCluskey, leader of Britain's largest trade union, Unite, described it as a "misuse of party funds" and has since hinted at a review of its spending ties with Labour.
Journalist Mr Hernon, whose book, Anti-Semitism and the Left, was published last year, told Express.co.uk: "Corbyn's reaction to Starmer's apology and compensation to the whistleblowers, when he said it was a political rather than a legal decision, I think was so appalling that Starmer should have started procedures to expel Corbyn from the Labour Party.
"He couldn't do that in the first two months of his leadership.
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Jeremy Corbyn said the payout was a political, rather than a legal decision
"But of course we are waiting for the EHRC report which I think is due out in September.
"If that shows that Corbyn was at the top of a racist and anti-Jewish regime then at that point I think Starmer would be justified in triggering a dismissal procedure."
Mr Hernon added: "Starmer is trying to heal some of the wounds and of course any moves against the sainted Corbyn would be very divisive.
"But once the commission report comes out it is better to have a quick civil war this year rather than let it drag on until we are approaching the next election.
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"If it was me I'd rather get it over with this year."
As for Mr McCluskey's suggestion that Unite would review its funding of Labour in light of the payout, Mr Hernon said: "Don't forget that my old mate Len has only got months to go.
"He should have retired about four years ago and he can't avoid retirement at the end of this year.
"The union bosses are not fools - they understand what happened at the last election. They want a Labour Government."
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Len McCluskey, General Secretary of Unite the Union
Mr Hernon, who says he considers himself "a proper lefty, not one of the bogus Momentum mob", believes it was his socialist credentials which resulted in him being commissioned to write a book critical of Mr Corbyn's time at helm of the party.
He said: "The Corbynistas just don't seem to understand what happened in the last election, with the Red Wall collapsing.
"Anti-Semitism may have been a small part, but it was a significant part.
"Northern working class families are the main recruiters for squaddies so the anti-Semitism segued into the pro-IRA stance that Corbyn and McDonnell had taken and you cannot do that with a family whose sons or perhaps grandsons have faced death in Northern Ireland.
Len McCluskey's tweet after the decision
"So that sort of blinkered, supposedly left-wing attitude covers both anti-Semitism and sharing platforms with terrorists.
"They always were living in la-la land but they simply blame the press and Brexit for what was a shattering defeat - the worst Labour defeat since 1935 I think.
"The 1983 Maggie landslide was under Michael Foot, who was a hopeless leader but nowhere near the scale of defeat that Labour suffered in December."
Assessing Sir Keir's approach since he was elected leader in April, defeating Rebecca Long-Bailey and Lisa Nandy in the process, Mr Hernon said: "He has done things very slowly, step by step which makes me think after the report it is feasible that he will move against Corbyn.
Boris Johnson, pictured returning to Number 10 after his election win, was branded a "clown" by Mr Hernon
"On the other hand Starmer although he resigned from the shadow cabinet in 2016 I think in protest at Corbyn's leadership, he went back and has stayed pretty quiet during the really heavy anti-semitism row of 2019 so there are a few doubts.
"At the moment he is dull - but maybe that's a good thing against the clown we have got as Prime Minister, who was fine bungling around on Have I Got News for You, but as Prime Minister during the COVID crisis not so much."
As for Labour's election prospects, he said; "The Red Wall seats in the north, a lot of them I know very well, loaned the Tories their vote and that was largely because of the Corbyn factor. They would like to vote Labour."
Express.co.uk has contacted Mr Corbyn to ask if he would like to respond to Mr Hernon's remarks.