Labour's leadership battle has intensified with a war of words over claims by deputy leader Tom Watson that "Trotsky entryists" were manipulating young party members.
Publicly the relationship between Mr Watson and Jeremy Corbyn has remained relatively peaceful despite Mr Watson telling the party leader he should stand down after 172 MPs backed a no-confidence motion in Mr Corbyn.
But the Labour leader's campaign team reacted furiously after Mr Watson accused "Trotsky entryists" of returning to the party and manipulating younger members to boost Mr Corbyn's chances of staying in post.
A spokesman accused the deputy leader of peddling "baseless conspiracy theories".
The falling-out came as Andy Burnham won the race to be Labour's candidate for Greater Manchester mayor in a 2017 election he will be widely expected to win, given the party's support in the city. But shortly after his victory, he found himself defending rebel MPs against a threat of mandatory reselection from one of the new pro-Corbyn members of the ruling National Executive Committee (NEC).
It came as Mr Watson suggested "Trots" are attempting to use Labour as a "vehicle for revolutionary socialism", are not "remotely interested in wining elections" and do not have the "best interests of the Labour Party at heart".
The deputy leader insisted he does not believe the vast majority of people who have joined the party and have been mobilised by the pro-Corbyn Momentum campaign group "are all Trots and Bolsheviks".
He told The Guardian: "Some of these people are deeply interested in political change, in building a more equal society, and are just on a journey in politics that they're new to, and I don't want them to feel that I'm labelling them, because I'm not.
"But there are some old hands twisting young arms in this process, and I'm under no illusions about what's going on. They are caucusing and factionalising and putting pressure where they can, and that's how Trotsky entryists operate. Sooner or later, that always ends up in disaster."