Momentum, the Labour leader’s pressure group, has repeatedly threatened to force centrist MPs to contest their candidacy ahead of the next general election.
And now three allies of Mr Corbyn have been elected to the national executive committee (NEC) of the Labour Party – putting more power in the hands of the party’s growing hard left.
Jon Lansmann, who founded Momentum, Yasmine Dar and Rachel Garnham stormed to victory in the recent NEC election, sweeping aside centrist candidate and comedian Eddie Izzard.
They will now be able to pressure the party’s rule-making committee on matters involving selection for candidates at forthcoming elections.
In response, panicked centrist MPs have vowed to abandon the party if they are threatened with deselection in order to make space for a more left-learning candidate.
They said they would prefer to sit as independents or even quit politics, sparking a wave of costly and risky by-elections which Labour could struggle to win.
One furious MP told The Times: “There’s no reason to wait it out. We would have no interest in toeing the line.”
Another said: “Corbyn has a lot to lose. If people start being deselected, what’s to stop them standing against him for leadership?”
The MP also said spurned MPs could simply find better jobs outside of politics, sparking by-elections Labour might not win.
They added: “If you want to look like a united government in waiting, the last thing you want is a whole load of bitter selection rows.”
Labour said last night they are only focusing on potential candidates in marginal seats held by other parties.
They did not comment on rumours sitting MPs could be forced to contest the right to defend their own seat.
A spokesman said: “Labour is currently focused on smelting candidates in the most marginal seats held by our opponents.
“Any other selections would need to be decided by the NEC.