One of Keir Starmer’s most vociferous critics has pulled out of the race to succeed Len McCluskey in a last-ditch bid to maintain the Left’s dominance over the Unite trade union.

Howard Beckett, who has called for Starmer to be removed as Labour leader, has withdrawn his candidacy for general secretary and swung behind fellow assistant general secretary Steve Turner instead.

The move is designed to maximise opposition to “moderate” candidate Gerard Coyne, who narrowly lost out to McCluskey in the race for the top job four years ago.

Beckett had been under huge pressure to pull out amid fears that having three prominent leftwing candidates would split the vote in the first-past-the-post election, leaving Coyne with his best ever chance of taking over the UK’s second biggest union.

In return for winning Beckett’s support, it appears that Turner will offer him a key post in the union should he win, possibly deputy general secretary.

A similar offer looks likely to be made to another Left contender, Sharon Graham, who has refused to withdraw.

In a joint statement, Beckett and Turner said they would have a “blended” manifesto which included ideas such as a new ‘Unite TV’ station to provide a progressive alternative to the news media.

“Throughout this contest, we have both been committed to one thing above all – developing further the role our union has played since its foundation as a fighting back, progressive, campaigning force for working people throughout Britain and Ireland.

“It is clear that developing that unique role requires the unity of the left in our union, and of all those representatives and members in the workplaces and beyond who have made Unite a union to be proud of.

“They will both work to implement a blended manifesto, taking the best ideas from both candidates, when Steve Turner becomes general secretary.”

Coyne reacted to the news by saying: “We now have a Communist Party candidate [Turner], a Socialist Worker Party candidate [Graham] and myself in the Unite election. I’m happy to be the mainstream candidate for the members.

“I am the only candidate who would change the culture of the union, make its financial affairs transparent, improve its internal democracy and end the ill-judged attempts to drive the Labour Party from the back seat.

“I was up against three full time officers of Unite who represented continuity and were opposed to change. Now their number is reduced to two. It makes no difference. It’s now clear that if you vote Turner, you get Beckett.”

On Friday, Beckett continued his attacks on Starmer, pointing out that “any other leader would be twenty points ahead” of the Tories in the national polls, and pointing to Labour’s tiny number of votes in the Chesham and Amersham by-election.

Earlier this week, he called unequivocally for demonstrations and protests outside Starmer’s office and Labour’s HQ to remove him as Labour leader.

However, Turner has previously told HuffPost UK: “Keir wasn’t my preferred candidate [he voted for Rebecca Long-Bailey]. But I’m a socialist, I’m a democrat, and the reality of it is he was elected by the vast majority of our members that voted.”

He had also warned that a split Left vote would help ‘centrist’ candidate Coyne.

“If everyone’s on the ballot paper, if there were a four way split, then that’s pretty much an open game. And who knows what the outcome of that would be.

“I think the centre vote would hold up because that’s a core vote, if that candidate played their cards right and ran a good campaign and not a negative campaign, absolutely I can see them getting 60,000 votes. And if we had the same turnout as last time, there ain’t enough votes to go round on a straight three-way split to defeat that.”

In their joint statement, Turner and Beckett said they would campaign together for the next two months to present a joint programme.

That included “greater support for workplace representatives, important new communications initiatives including Unite TV, upgraded education and training for members, an independent and progressive political voice, and a new structure for the union reflecting the diversity of our nations and regions.”

Turner said he warmly welcomed Beckett’s support and appreciates his decision to stand aside. “As general secretary two of the most important people in his team will be Howard Beckett and Sharon Graham and the structures of Unite would reflect this.”

Coyne is adamant he can still win, and has denounced the “backroom deals” aimed at pushing a “continuity candidate” to succeed McCluskey.

Sharon Graham said: “The announcement of the Turner/ Beckett ticket, along with the Gerard Coyne candidacy, now completes the Westminster Brigade. I am the Workplace candidate and will be standing to ensure the voice of Unite members is heard.

“The union must return to doing what it says on the tin – fighting for jobs pay and conditions. The two other candidates offer no more than the settling of old scores and the interest of Westminster politics . It is the Westminster brigade versus the workplace now”.

Despite recent cuts in donations, Unite is still Labour’s biggest financial backer and has huge influence on the party through its representatives on the ruling National Executive Committee (NEC).

Beckett was recently suspended by Labour after he tweeted that home secretary Priti Patel should be deported for her treatment of migrants and asylum seekers.