Unite boss Len McCluskey has described as “ridiculous” claims by Labour deputy leader Tom Watson that his union is involved in a “secret plot” to help a left-wing group take over the party.
Mr Watson has accused Unite of planning to fund activist group Momentum, which he said could “destroy” Labour.
But Mr McCluskey said the claims were “a complete fabrication” and “there are no plans to fund anybody”.
Labour leader Jeremy Corbyn faced hecklers as he urged his MPs to unite.
The row follows comments made by Momentum’s Jon Lansman, who was reportedly taped saying Unite could affiliate to his group rather than just to Labour.
Mr Watson said he had a duty to “call out” what appeared to be a “secret plan” to take over the Labour Party, which “threatens our very existence as an electoral force in the land and it needs to stop”.
He urged Mr McCluskey to publicly state Unite would not fund Momentum if he was re-elected as Unite leader.
But Mr McCluskey said he had “not met Jon Lansman – there have been no secret meetings with anybody about Momentum”, and he accused Mr Watson of “a deliberate attempt to sensationalise something in order to influence the outcome of the general secretary election of Unite”.
“Really, Tom and the other right-wing Labour MPs would be best keeping their nose out of our business because the truth of the matter is, my members will reject any attempt from outside bodies to influence and to try to take over Unite – it won’t work,” he said.
‘Party within a party’
The Unite boss spoke out at the same time Mr Corbyn addressed an “explosive” meeting of the Parliamentary Labour Party (PLP), where there was shouting over the leadership’s handling of the issue, with one Labour MP referring to Mr Corbyn as “a so-called leader”.
Mr Watson was “cheered to the rafters” as he arrived at the gathering, with senior figures in the party challenging claims he had been isolated and condemned at a “robust” earlier meeting of the shadow cabinet, which prompted Mr Corbyn and his deputy to issue a joint statement agreeing to strengthen party unity.
An aide to the Labour leader denied briefing against Mr Watson and said Mr Corbyn’s message had been on the need for the party to talk about the issues which affect Labour voters – not internal issues within the Labour party.
It is understood the chairman of the PLP warned that Momentum was operating as a “party within a party” after hearing a tape of Momentum founder Mr Lansman reportedly urging supporters to change the nature of the Labour party.
One senior peer, who is a veteran of earlier internal battles, said it was “like 1985 all over again”, while another senior peer said it was “much worse than that”.
The BBC’s assistant political editor Norman Smith said the renewed infighting was potentially “catastrophic” for Labour, coming in the wake of the Copeland by-election loss.
Change of direction?
In the recordings, which were revealed by The Observer newspaper, Mr Lansman said: “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.”
He went on to tell activists it was “absolutely crucial” that they secured a change to the party’s rules to ensure that whenever Mr Corbyn stands down, they are able to get a candidate on to the ballot paper to succeed him.
Ahead of Monday’s meeting, shadow chancellor John McDonnell said Mr Watson’s comments were “disappointing” and suggested he was trying to influence the outcome of the contest for Unite leader – in which incumbent Mr McCluskey – a supporter of Mr Corbyn – is being challenged by Gerard Coyne.
The ballot papers for the contest will be sent out later this week, with the result to be announced next month.
The election is being seen as a proxy battle for control of the Labour movement. Most Unite branches have backed Mr McCluskey in his bid to be re-elected.
Christine Shawcroft, a member of Momentum who sits on the party’s National Executive Council, said Mr Watson was “rather right-wing” and wanted to return to a “command and control” system for running the party based on a “Blairite model”.
She rejected suggestions Momentum was a hard-left entryist organisation trying to infiltrate Labour, describing the terms as “silly labels”.
“Jon said nothing that was at all controversial, but I think this is a concerted attempt to interfere in the internal election in Unite for general secretary, which is really shocking.”