Keir Starmer wants to abolish the House of Lords and replace it with an elected chamber if he becomes Prime Minister.
The Labour leader would bring in major reforms in the first term of a Labour Government to "restore trust in politics" after rows over Tory PMs handing gongs to "lackeys and donors".
Boris Johnson triggered fury with attempts to stuff the Lords with allies, including media mogul Lord Lebedev. The son of an ex-KGB agent was given a life peerage in 2020 but he has spoken just once on the floor of the House.
Mr Johnson has also faced accusations that he has proposed several Tory MPs for peerages but told them to delay accepting them to prevent triggering by-elections.
The Mirror has long campaigned for the unelected House of Lords to be abolished, and Labour pledged to do so in its 2019 manifesto. Mr Starmer also repeated this pledge in his leadership campaign.
The Lords has swelled in size in recent years despite efforts to slim down the upper chamber to bring it closer in line with the Commons.
Shadow Work and Pensions Secretary Jonathan Ashworth said it was time to "democratise" the Lords.
He told Sky News: "There's lots of great expertise in the House of Lords and lots of very good people in the House of Lords but we need to bring it into the 21st Century.
"It needs to be a modern second chamber and there it should be elected. I think trust in politicians is so low because of the actions of Boris Johnson."
Mr Starmer told Labour peers that part of the reason for reform was the public "have lost faith in the ability of politicians and politics to bring about change", according to the Observer.
Labour would hold a consultation on the composition and size of a new chamber following longstanding arguments about the soaring number of peers.
Under the plans, the Lords replacement would be "truly representative" of the UK's nations and regions while still retaining its role as the second chamber in relation to the Commons.
It comes as it emerged that Mr Starmer had been taking advice from Tony Blair and Gordon Brown as he gears Labour up for government.
After the chaos of recent weeks triggered by Ms Truss's disastrous mini-budget, Labour remains ahead in the polls despite the arrival of Rishi Sunak into No 10.
Mr Starmer said: "I've been talking to Tony Blair and Gordon Brown for some time now.
"I'm conscious that we've been out of power for 12 years. That means I don't have people around the shadow cabinet table who've got huge experience in government. So, I'm determined that we need to be ready to hit the ground running."
