The leader of Britain's biggest trade union has hit out at the "cabal" of Labour "malcontents" he said were plotting against party leader Jeremy Corbyn.
Len McCluskey, general secretary of Unite, challenged Mr Corbyn's critics to embrace the "much-needed change" his leadership offered.
In an address to the Oxford Union, he said Labour MPs and others should concentrate on taking the fight to the Tories instead of "scheming" against their own party.
Mr McCluskey said the Labour leadership election saw an "exhausted New Labour" collide with rising public discontent about the inability of business-as-usual politics.
"Some have sought to excuse their disloyalty to Corbyn by pointing to his own rebellious past on the backbenches.
"But who can seriously argue that his votes in parliament against the Iraq war, identity cards or university tuition fees now diminish his ability to lead the Labour party today?
"On all these issues he was not only right, I believe, he was giving voice to the views of most Labour supporters.
"I'm not saying that any Labour MP should have to abandon his or her own views, or cease to articulate them within the party's democratic structures.
"But I am saying that this continual war of attrition is achieving nothing beyond taking the pressure off the Government.
"So my clear message to the plotters is - stop the sniping, stop the scheming, get behind Jeremy Corbyn and start taking the fight to the Tories."
The Unite leader said MPs who refuse to accept the overwhelming mandate Jeremy Corbyn got from Labour's membership were described as the "moderates" in the party.
He added: "It's an abuse of language - there is nothing "moderate" about voting to bomb Syria or agreeing more public spending cuts, anything more than it's "extreme" to vote for peace or for an end to eye-watering austerity."
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