The news that 70 Tory MPs, including four select committee chairmen and three former ministers, have signed a letter  (£) vowing to rebel over House of Lords reform means that the government is almost certainly heading for defeat in tomorrow night's vote. Even if the whips manage to talk some MPs round, the rebels only need 51 to defeat the programme motion, which would place a 10-day limit on debate. Labour, which plans to support the bill at its second reading, has also pledged to vote against the timetable motion. As a result, David Cameron is facing his first defeat on government business in the Commons.
With no time limit on debate, the rebels will aim to talk the bill into the ground, something that Downing Street's decision to rule out a referendum  will do nothing to discourage. The upshot is that Lords reform is almost certainly doomed.
The key question for the coalition's future is what form the Lib Dem retaliation takes. If Nick Clegg demands the abandonment of the boundary changes , a split is no longer unthinkable.
The full text of the letter is below; the three former ministers who signed are Malcolm Rifkind, David Davis and Peter Lilley.
We come from all sides of the Conservative Party, and are writing as reformers to express our serious concern at the current proposals to create an elected House of Lords. It threatens to pile a constitutional crisis on top of an economic crisis
What is now proposed will undermine the primacy of the Commons, with competing chambers which will lead to legislative gridlock.
It will create hundreds of unaccountable new elected politicians at a time when we as a party are committed to reducing the cost of politics; and
It will produce a chamber which is less expert, less diverse and significantly more expensive than the present one.
The commitments in our 2010 election manifesto and in the Programme for government - to seek consensus and to bring forward proposals - have been fulfilled. We hope you will support us in giving this Bill the full and unrestricted scrutiny it deserves.