The rules which were responsible for Mr Corbyn becoming party leader in 2015 are set to be torn up. The one member, one vote system will be replaced by a series of weighted voting.
Returning to Labour’s old system, used in elections prior to 2015, MPs, party members and trade unions would each represent a third of the votes for a new leader.
Ed Miliband changed the system in 2014 to instead give all members of the party a single vote for a candidate, each of equal value.
The system favoured Mr Corbyn whose popularity among the grassroots saw him overwhelmingly elected as leader in 2015.
Sir Keir briefed his shadow cabinet of his plans to reverse the rules change yesterday and will today set them out to trade union leaders.
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“Our rules as they are right now focus us inwards to spend too much time talking to and about ourselves, and they weaken the link with our unions,” Sir Keir said.
“I know that this is difficult – change always is – but I think these changes are vital for our party’s future.
“These are two things that have got to change if we are serious about winning the next election.”
His plans have already sparked outrage among some factions of the Labour Party, who accuse Sir Keir of undermining democracy.
Former shadow chancellor John McDonnell said: “Labour leadership aims to bounce through conference return to electoral college giving Parliamentary Labour Party one third of votes in leadership election.
“Critical Labour MPs make it clear they reject this proposal and reassert right of members to elect leader.”
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While Sir Keir aims to use the coming days to persuade unions to back the change of rules by highlighting how it would give them a greater say, there has so far been little support.
Unite’s general secretary Sharon Graham said the proposal to ditch the current system is “deeply disappointing”.
Meanwhile, the TSSA transport union accused Sir Keir of “gerrymandering”.
Changes to the rules for leadership elections will need to be voted on at Labour’s annual conference taking place this weekend.
With outrage among some MPs and members at the proposed scrapping of the one member, one vote system, any ballot on the changes is likely to be extremely close.
It sets Sir Keir up for an almighty fight against aspects of his own party during the same weekend he is hoping to reboot his leadership.
The Holborn and St Pancras MP has not given an in-person speech to Labour members since becoming leader due to the pandemic.
He is hoping to use his address to the conference as a chance to unify the party and present a clear vision for Britain.