The leader of Unite, Len McCluskey, has been praised by left-leaning Labour MPs for ordering a review of the union’s political donations after Keir Starmer’s decision to pay damages to former staff turned antisemitism whistleblowers. Ian Lavery, the party chair under Jeremy Corbyn, is one of three former shadow ministers who have told the Guardian they support the union’s general secretary for re-examining whether to donate to Labour in the wake of the six-figure settlements. Their interventions will increase tensions between the Socialist Campaign Group of MPs and Labour’s leader following the latter’s decision to apologise and pay damages to seven staff who claimed they had been defamed by senior party figures after taking part in a BBC Panorama documentary on antisemitism. It comes amid growing speculation about the future leadership of the UK’s three biggest unions – Unite, Unison and the GMB – which are responsible for a majority of Labour’s funds. McCluskey, whose union has given Labour around £7m since January 2019, said on Saturday that paying the damages was an “abuse of members’ money”. He told the Observer: “A lot of it is Unite’s money and I’m already being asked all kinds of questions by my executive. It’s as though a huge sign has been put up outside the Labour party with ‘queue here with your writ and get your payment over there’.” Lavery, who was also shadow minister for trade unions under Corbyn, said: “What Len says is extremely important. I have had people asking me from Unite if it is right that members’ money is used to finance Keir’s legal challenges and pay compensation when the advice that the party allegedly had was that the party was in a very strong position to defend the claims. “People have got to be accountable and responsible. You cannot expect unions to pump millions of pounds into the party if the party isn’t accountable.” Another former shadow cabinet minister agreed: “Starmer is on warning that he must work with everyone across the movement and cash has to be accounted for. The lurch to the right will not be paid for with union subs.” Another said: “Len said what a lot of us have been thinking.” The party settled with the ex-staffers as part of an attempt to draw a line under the antisemitism row. However, Labour officials warned the shadow cabinet last month that mounting legal action related to antisemitism could cost the party hundreds of thousands of pounds over the next year. One Starmer loyalist dismissed McCluskey and Lavery’s criticisms. “They are fighting a battle over antisemitism they could not win when they were in charge and now they want Keir to make the same mistakes. It is a silly position to take and deeply insulting for many Jewish members,” they said. McCluskey, 69, also said he intends to stay in charge at Unite until his tenure ends in 2022, amid growing speculation he could stand down early as well as electioneering from some of his close union allies. Meanwhile the Unison leader, Dave Prentis, has announced that he will be stepping down at the end of the year, while Tim Roache stood down as general secretary of the GMB in April amid allegations of misconduct. The “Big Three” unions, which represent more than 3 million workers, not only contribute most of Labour’s funds, but also sponsor MPs and influence votes on policy and party rules. Although the top of the union movement is still dominated by middle-aged white men, there are female or BAME candidates standing for each position. Speculation McCluskey may step down had increased after United Left, the faction which has dominated Unite, held a ballot last month and decided to back the union’s assistant general secretary, Steve Turner, to become the next leader. Sharon Graham, Unite’s organising director said to be separate from McCluskey’s inner circle, is also planning to stand. After the GMB announced it had received an anonymous letter containing claims about Roache’s conduct, the union asked a QC to launch an independent investigation into allegations of wrongdoing. Roache vehemently denies the allegations. Nominations for his successor will close next month. Rehana Azam, the union’s national secretary who has co-ordinated its response to the Covid 19 crisis, is expected to be a popular frontrunner. Gary Smith, the union’s secretary in Scotland, is also expected to stand. The inquiry, conducted by Karon Monaghan QC, is expected to hang heavy over the election, following claims that other executives and staff were involved in inappropriate spending. The union said: “The need for a full, transparent and independent investigation following a number of very serious allegations made by way of anonymous correspondence received by the union has been agreed.” In a statement released in April, Roache said: “I have spent 40 years defending people based on evidence and the right to natural justice. This anonymous letter affords me neither.” Candidates standing for the top job in Unison, where two-thirds of members are women, include Margaret Greer, who would become both the first female and the first black general secretary of the UK’s biggest union if she wins. Glasgow-born Christina McAnea, who is currently assistant general secretary, is also standing. Two other BAME candidates are also standing. Roger McKenzie, an assistant general secretary who is on the left of the union, and Hugo Pierre, a Socialist party member. Nominations open on 10 August.