LABOUR chiefs were fighting among themselves again yesterday after deputy leader Tom Watson warned that the UK’s biggest union has a “secret plan” which will “destroy” the party.

Speaking on BBC Radio 4, deputy leader Watson accused pro-Jeremy Corbyn activists of trying to “take control”, saying: “I regard this as a battle for the future existence of the Labour Party.”

Watson warned a tie-up between grass-roots group Momentum and Unite, the party’s biggest donor, could “destroy” Labour and said he would raise the issue with party leader Corbyn.

Raising fears of entryism, he went on: “Enough is enough, this has to stop. There are some people who do not have our electoral interests at heart.”

The comments follow claims that the Momentum group, which backs Corbyn, aims to secure financial backing from Unite. Jon Lansman, who heads the group, was allegedly taped saying he expects Unite, which is currently affiliated to Labour, to align with Momentum if Len McCluskey is re-elected as general secretary in a vote due to begin on Monday.

Watson, who fears entryists are trying to wrest control of party structures for their own ends, said he would discuss the issue with Corbyn, saying: “I don’t know what he knows and doesn’t know.

“This is high stakes. What Jon Lansman has outlined is a plan with Len McCluskey, the leader of Unite, to take control of the Labour Party.”

John McDonnell, the shadow chancellor, reacted by accusing Watson of waging an “internal battle” over the direction of the union, stating: “This is not civil war.

“It’s all about Tom and the internal battle he is trying to wage within Unite. Dragging the party into this is disappointing.”

Gail Cartmail, the acting general secretary of Unite, called Watson’s claims “extraordinary” and “entirely inaccurate”, stating: “As Unite has made it clear, it is exclusively for our executive council to determine which organisations we affiliate to.

“There are no plans for Unite to affiliate to Momentum. For the record, Len McCluskey has never met Jon Lansman to discuss this or any other matter.

“It is extraordinary that the deputy leader of the Labour Party should interfere in Unite’s democracy in this way.”

Christine Shawcroft, Momentum director and a member of Labour’s national executive committee, said Momentum would work with any organisation that wished to affiliate to it. She added: “It’s no threat to the position of the Labour Party and the strength of the Labour Party.

“The only thing it might destroy is people who feel entitled, in a very undemocratic way, to control what the members are able to vote on in the end.”

Speaking on the Today programme, Shawcroft went on: “We have a mass membership now and it wants its voice to be heard.

“There is a democratic deficit in the Labour Party where the structures we have do not reflect the support for Jeremy Corbyn that has been shown by the mass of the members”.

McCluskey looks like to be re-elected by members, with nominations from 1185 Unite branches.

He has five times the declared support of challenger Gerard Coyne, the union’s West Midlands organiser.

The voting period runs from March 27 to April 19, with two days of counting and scrutiny to follow before the winner is announced.