Labour’s biggest union backer will review its political donations in light of Keir Starmer’s decision to pay damages to ex-staffers who claimed the party had not dealt with antisemitism, its general secretary has warned. In an interview with the Observer, Unite leader Len McCluskey said there was “no doubt” the union’s ruling executive would be demanding a review of the millions it donates to the Labour party in the wake of the six-figure settlements. “It’s an abuse of members’ money,” he said. “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’. McCluskey’s robust intervention will intensify the infighting prompted by the party’s decision to apologise and pay damages to seven staff who turned whistleblower for a BBC Panorama documentary on antisemitism. The party accused them of acting in bad faith, but settled as part of an attempt to draw a line under the antisemitism row. Former leader Jeremy Corbyn condemned the payouts. Any loss of financial support from Unite would pose a major problem for Labour. While its large membership provides some income, the union remains its biggest donor by far. It has given the central party more than £7m since the start of 2019, according to Electoral Commission records. In a wide-ranging interview, McCluskey put Starmer on notice that he would fight any shift to the right. He said it would “constitute a problem” if Starmer edged away from his 10 leadership campaign pledges, which included Corbyn-era policies such as higher taxes on the wealthy, abolishing tuition fees and “common ownership” of rail, mail, energy and water. “He has to recognise that the ship he is sailing, if it lists too much to the right, will go under,” he said. “We’ll have to wait to see how the situation unfolds. Unite is financially a very powerful and strong union. We have a political fund that is the largest in the whole of Europe. So of course, my members would expect that we are influential in that respect. There will be some interesting debates and discussions in the coming months with Keir, not only for myself but all the unions on the left who are equally in a situation at the moment where they’re wondering where we are, what direction are we going.”He also warned Starmer against the timidity that he says sank Ed Miliband’s leadership. “There’s nothing wrong with caution, so long as that doesn’t slip into fear or timidity,” he said. Following suggestions that the left has lost power and influence since Corbyn’s departure as leader, McCluskey revealed that figures across the left would gather for a major event this autumn. “I don’t see the creation of an alternative party to Labour. But I do think it is the duty and the legitimacy of the left to continue to argue for our views and our thoughts and our policies.” He said Starmer had to ensure he was including the left. “He seems to me to be really genuine about wanting to unite the party. But my message to him would be, you need to start making certain that you reach out the hand to the left – that they are an integral part of his thinking.” McCluskey denied reports that he would step down from his role earlier than expected. “My period in office finishes in April 2022 and I’ll be in charge until then,” he said. “This next six- to 12-month period is going to be very, very crucial in industry. That’s my main priority – and of course that spills over into politics, because what the government does, what Labour is campaigning for, matters.”