As was rumoured this morning, David Cameron has now dropped the programme motion on House of Lords reform, which would have limited debate on the bill to 10 days. With upwards of 70 Tories prepared to join Labour and vote against the motion, there was no hope of it making it past the Commons. In withdrawing the motion, Cameron has merely brought forward the government's defeat.

The second reading vote will still go ahead and, with the support of Labour, the bill will proceed with a large majority. But unless the government introduces a guillotine motion at a later date, the risk remains that MPs will talk it into the ground.

The upshot is that the fate of Lords reform now rests in Labour's hands. If Ed Miliband's party agrees to support closure motions to limit debate on the bill, the legislation could yet make it through the Commons. Responding to Cameron's move, Sadiq Khan has pledged that Labour will do all it can "to ensure the bill progresses". The party's opposition to the programme motion was not, he said, a "wrecking tactic" but an attempt to improve an "inadequate bill".

As Khan's words imply, Cameron and Nick Clegg will need to offer concessions in order to win his party's support. The most obvious would be a referendum on Lords reform, as proposed by Labour in its 2010 manifesto. This would have the added benefit of placating at least some of the Conservative rebels, such as Nadhim Zahawi and Rory Stewart, who have said they would be prepared to support the bill were a public vote promised. Others, flushed with success after the AV campaign, simply want the chance to give Clegg another bloody nose. (We must hope the voters decide otherwise.)

The Lib Dem leader has always resisted a referendum on the grounds that all three of the main parties supported reform in their manifestos. But with parliament divided, he will find it hard to argue that the people should not be given a say. Tonight, a referendum looks like the only way to avoid yet another defeat for reform.