Labour leadership candidate Rebecca Long-Bailey is set to reveal her support for open parliamentary candidate selections in a key policy announcement at a London rally on Tuesday evening.

Unveiling her plans for democratising the Labour Party, the Shadow Business Secretary will endorse the rule known as ‘mandatory reselection’ whereby sitting MPs must seek local approval before each election.

Currently, if a sitting Labour MP wishes to restand for their seat and there is no snap election, local party branches and affiliates vote in a ‘trigger ballot’ to either approve or refuse automatic reselection.

Unless more than a third of party branches or affiliate branches vote in favour of ‘triggering’ their local MP, no full selection process is held and the incumbent becomes a parliamentary candidate again.

Long-Bailey is expected to tell supporters at her sold-out event that she backs the introduction of full selection processes, as well as “democratic policy making at every level” and “properly resourced political education”.

Setting out her case for the party reforms, the leadership contender will say: “It’s true that the pace of democratisation in our party has been too slow. And that runs from how we develop our policies to how we select our candidates.

“Now is the time to break out of the bunker and become the open, democratic party we’ve always aspired to be. My role as leader is to democratise the party and to examine new ways to empower our members, trade unions, MP’s, leaders and councillors.

“This means open and democratic policy making at every level, properly resourced political education and a professional and accountable party operation. These are the basics.”

Explaining her reasons for endorsing open selections, Long-Bailey will argue that Labour must “rip up our outdated rule book that has held back our members for too long and throw open the door to a new generation of MPs and candidates”.

The leadership hopeful will add: “Being an MP or elected representative is a privilege that must be earned, and I want to open the discussion now on how our candidates should be selected, how we nurture and bring through talent in our movement, whilst recognising and valuing the experience of sitting MP’s.

“We all know that person. That talented, selfless and hardworking person who’d make a brilliant MP but would never dream of putting themselves forward. It’s those people I want to raise up.

“ The collective knowledge and experience of our movement is Labour’s greatest strength. Now is the time to unleash it. And that’s why I support open selections for parliamentary candidates.

“We need a democratic revolution – both in the country and in our party. Our party must lead by shining example. If we can’t democratise our own party, we will never be trusted to democratise workplaces, our economy and the country.”

Mandatory reselection was a central demand of Bennites and left-wing lobby group the Campaign for Labour Party Democracy (CLPD) throughout the 1970s. Corbynite network Momentum, which is backing Long-Bailey’s leadership bid, came out in favour of the idea in 2018.

Asked for comment on Long-Bailey’s fresh announcement, a spokesperson for Keir Starmer said: “Keir will be setting out his plans to democratise the Labour Party in the coming weeks.”

In a recent interview with LabourList, the Holborn MP and leadership frontrunner said he was “not against the principle” of mandatory reselection and that “there has to be a process by which it’s possible to challenge sitting MPs”.

Labour members can expect to scrutinise all candidates’ plans for internal democracy at upcoming party hustings, such as in Leeds on Saturday, as well as the Open Labour/Electoral Reform Society hustings in Nottingham on Sunday.