Jon Lansman, one of three Momentum candidates elected to Labour's national executive last week, insists there is no hit list including high-profile MPs such as Hilary Benn and Angela Eagle.
"We have made it clear that we are not going to campaign to de-select anyone, at all, anywhere," he said in an interview with The Independent.
"Momentum nationally is not going to campaign to deselect any MP and we will stick by that. We are not going to campaign to deselect any individual MP."
Mr Lansman claims a Sunday Times report last weekend about a "deselection hit list" of MPs critical to Mr Corbyn had "no factual basis whatsoever".
But in a warning that will alarm some Labour MPs, he says it "wouldn't be surprising" if local constituency parties use a trigger ballot process to ditch MPs who don't try to perform well.
"No Labour MP that works hard and campaigns and listens to their members has anything to fear from the selection process," Mr Lansman - a former aide to Tony Benn - adds.
The Sunday Times claimed up to 50 Labour MPs are on a Momentum hit list and that a Labour whip has told moderate MPs not to rock the boat or they could face deselection.
Neil Coyle, a critic of Mr Corbyn who has been the target of Twitter attacks by supporters of the Labour leader, told The Independent that Mr Lansman's comments were welcome.
But he added: "Lansman's real challenge is in ensuring Momentum members at local level adhere to his commitment."
Chris Leslie - an anti-Brexit rebel named on the reported deselection hit list - said: "The Momentum leadership are constantly obsessing about process.
"It is an attempt to instil fear into every single member of the Parliamentary Labour Party, whether they are on the frontbench or the backbench, that the threat to their job is always there if they dare disagree."
At the meeting of the Parliamentary Labour Party on Monday, Mr Leslie challenged chief whip Nick Brown on The Sunday Times claims, but Mr Brown said there was no deselection hit list.