Labour deputy leader Tom Watson today traded blows with the party's former communications chief over its stance on Brexit, telling Alastair Campbell: "You no longer decide Labour party policy".
The pair went head-to-head on ITV's Peston On Sunday, with the former spin doctor for Tony Blair blasting the current Labour leadership for leaving the door open to backing Theresa May's final Brexit deal.
Mr Campbell, who now edits the anti-Brexit New European newspaper, said "none" of Labour's tests for a "jobs-first" Brexit looked set to be met by the deal Mrs May will bring to Parliament.
"I think the Labour Party should actually follow the logic of that through now and start campaigning clearly in saying that the Brexit deal that she's bringing back - there's no way that Labour can support it if those tests are to mean anything," he said.
But Mr Watson shot back, saying the former director of communications for Number 10 used to be a "sort of party communications officer", and insisting: "We have to listen to the whole of the British people on this, Alastair.
"And we've got to make sure that we honour them by saying we're coming out of the EU."
However, Mr Campbell said that position meant Labour could end up backing the Government on Brexit "whatever the costs, whatever the consequences".
"That is crazy," he fumed.
That comment prompted a withering put-down from Labour's deputy leader, who told Mr Campbell: "What I'm saying is you no longer decide Labour party policy. I'm sorry about that. I know you'd like to."
Mr Watson also took a jibe at Mr Campbell's current job, saying: "I know they don't pay you a lot of money as editor of the New European. You know, you probably want George Osborne's job [as editor of the Evening Standard] as a former person who used to be involved in politics."
The ex-Labour communications supremo replied: "I'm happy where I am. But what I'm not happy with is where you're pretending you're doing something different if you're basically in the same position whatever happens."
The on-air spat came amid a heated row in Labour over the party's stance on a so-called Norway-style Brexit.
Senior Labour figures have given mixed signals on whether the party could lend its support to continued membership of the European Economic Area (EEA), a move that would effectively keep Britain in the Single Market.
Some of the party's MPs believe backing EEA membership provides the best chance of softening the economic impacts of Brexit.
Pressed on the party's stance today, Mr Watson said: "We haven't decided our whipping arrangements yet - that will be decided at a future Shadow Cabinet.
"But we've been pretty clear that the sort of model that applies to Norway, yes it has some benefits, but it also has some disbenefits not least that it makes sure, there's no reform of workers movements across Europe."