Len McCluskey, the left-wing leader of Unite, has warned that it would be “a mistake” for Labour to take its financial contributions “for granted” following the decision to pay damages to antisemitism whistleblowers.

Mr McCluskey, in an interview with The Observer, stated that there was “no doubt” that the Unite executive would seek a review of its funding of the party.

He claimed that much of the six-figure damages that had been awarded to the seven whistleblowers who spoke to the BBC’s Panorama in July 2019 had come from Unite funds.

“It’s an abuse of members’ money,” said Mr McCluskey, a key supporter for former Labour leader Jeremy Corbyn.

The whistleblowers had sued the party after it accused them of acting in bad faith and, despite claims that Labour would ultimately be unsuccessful in court, Mr McCluskey stated that he felt the settlement was “quite extraordinary”.

He added: “There were lots of claims and criticisms that the Labour Party was institutionally antisemitic. I absolutely reject that.”

Speaking on Radio 4’s Today on Monday, Mr McCluskey doubled down, saying “my executive will want questions answered” over the use of the money and dubbed the decision to settle “a clear miscalculation”.

In July, it was revealed that Unite's legal chief Howard Beckett had provided "practical support" to Labour members "purged" as part of the party's antisemitism "witch-hunt". 

Unite is Labour’s largest union backer and any reduction in its funding for the party would pose serious problems.

Then union has provided Labour with over £7 million since the beginning of 2019, according to Electoral Commission figures.