Tom Watson has said a plan by the left-wing group Momentum to take control of Labour has started a “battle for the future existence of the party”.
Jon Lansman, the founder of the grassroots organisation that supports Jeremy Corbyn as leader, was secretly recorded addressing supporters at a meeting in Richmond, south London, earlier in the month.
On the tape, which was released by the Observer, Lansman says its supporters need to make sure the left is far better represented in key positions at all levels of the party.
He also discusses an affiliation with the Unite union, the largest trade union in the UK and Ireland.
In the recordings Mr Lansman says: “Assuming that Len McCluskey wins the general secretaryship, which I think he will, Unite will affiliate to Momentum and will fully participate in Momentum, as will the CWU.”
However, speaking on BBC Radio 4’s Today programme, Watson said the plot could destroy the Labour party.
“Enough is enough, this has got to stop… I’m afraid there are some people who do not have our electoral interests at heart,” he said.
“I regard this as a battle for the future existence of the Labour party,” he said. “This is high stakes and I hope my fellow members are going to understand that.”
“We have never seen the biggest union organising a political faction in the Labour Party with the tacit approval of the leadership”.
Watson called on Corbyn to “deal” with Lansman, although stopped short of saying he should be removed from the party.
“Len McClusky has to show responsibility, too,” he added. “We could do with him trying to understand how important this is.
“We cannot have powerful people like Lansman saying secret plans to control the Labour party may be disrupted by a general election. Our sole focus has to be a general election.”
Those on the “soft-left”, centre and right of the Labour party say this affiliation would amount to a huge shift of power and financial resources to pro-Corbyn members.
Through the deal, Momentum, founded four weeks after Corbyn’s successful campaign for the Labour Party leadership, would hope to secure the long-term direction of the party.
Also speaking on Today, Christine Shawcroft, a member of Momentum, said Labour’s MPs could not have a “veto” on the wishes of the membership when the time came to electing Corbyn’s successor.
“We have a mass membership now and it wants its voice to be heard,” she said. “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”.