Rebels told to toe line on Lords

Reforms threaten to swamp the coalition's legislative programme

David Cameron is battling to save the coalition's legislative programme from being swamped by months of debate on House of Lords reform, with potential Tory rebels being warned that voting against the Government will harm their chances of promotion.

Downing Street is desperate to prevent defeat in a vote on Tuesday that will decide whether or not the Government is able to impose a time limit on debate on the plans for a slimmed-down second chamber of around 450 elected senators.

Labour has said it will vote against the motion, arguing the reforms should be debated fully. However, it would pave the way for weeks of late-night sittings reminiscent of the Maastricht Treaty debates in the early 1990s. Up to 100 Tory MPs were said to be ready to rebel, although that number is thought to have fallen in recent days.

The issue has sparked a row, with Richard Reeves, who left his job as Nick Clegg's adviser last week, warning that if Tories blocked the reforms they could not count on Lib Dem support for plans to redraw constituency boundaries which would benefit the Conservatives. Tory MPs lined up to condemn the "blackmail".

Last night a senior Lib Dem source hit back: "Being accused of treachery by some of these serial rebels on the Tory back benches is like being accused of being over-theatrical by Mario Balotelli. These people who rarely vote with the Government are now trying to complain about betrayal."

Tory rebels have seized on the wording of the coalition agreement, which promised to "establish a committee to bring forward proposals for a wholly or mainly elected upper chamber on the basis of proportional representation".

However David Laws, the Lib Dem former cabinet minister who negotiated the deal, insisted the agreement was not just to draw up but also to pass such legislation. He told The Independent on Sunday: "There was no confusion in our talks on this. There was strong agreement from both sides that Lords reform needed to happen. A deal is a deal. Once you get a situation where a party is going to pick and choose from the coalition agreement, it is very destabilising." It would be "madness" for the Government to become stuck in a "swamp" of never-ending debates on a policy promised in both the Tory and Lib Dem manifestos, he added.