Momentum is understood to be preparing to throw its weight behind sweeping changes that will make it far easier to unseat serving Labour MPs ahead of party conference in Liverpool next month.
The organisation is likely to back a number of motions that will enable members from local parties to challenge sitting MPs.
Red Roar reported this week that two motions – put forward by Labour International and Young Labour – will change the rules so that a challenger can emerge at the start of the selection process.
Under existing rules sitting Labour MPs have to be removed in a trigger ballot before new candidates can emerge.
Momentum’s decision to back an overhaul of party rules means the proposed changes are more likely to make it to conference floor. If they are approved in Liverpool a significant number of Labour MPs could face challenges from party members ahead of the next election.
Momentum’s owner and founder Jon Lansman has spent his political life campaigning for greater democracy in the party and calling for Labour members to be handed more power.
But the move, which could be announced as early as tomorrow, will be regarded by many Labour MPs as a hostile act.
Momentum wants to encourage activists from the grassroots to stand for election, but there is little doubt the rule changes would pit members from the left of the party against established MPs.
It will infuriate the PLP, which has repeatedly urged Jeremy Corbyn to refrain from introducing mandatory reselection.
In the week Frank Field resigned the Labour whip, citing aggression and intimidation within his CLP in Birkenhead, Momentum’s decision to support the most fundamental changes to selection rules for many years will confirm the suspicions of many Labour MPs that they are regarded by the leadership of the party as obstacles to be removed.
Momentum is expected to frame its support for the changes as part of an attempt to bring new blood into the party and reinvigorate the ranks of MPs.
But for the majority of dedicated and long-serving Labour MPs who have been on the frontline of a brutal civil war in the party for the last three years, it will merely confirm that they are regarded by Jeremy Corbyn’s allies as the enemy within.