The row over House of Lords reform claimed its first government scalp early on Tuesday evening when Conor Burns resigned as a junior member of the coalition.
Burns, a ministerial aide to Northern Ireland secretary Owen Paterson, told MPs that he could not support the House of Lords Reform Bill at second reading, a vote scheduled for 10pm the same evening.
The MP for Bournemouth West is one of two junior members of the government who have indicated that they cannot support Nick Clegg's plans to turn the Lords into a largely elected chamber.
Angie Bray, who is parliamentary private secretary to the Cabinet Office minister Francis Maude, also confirmed to The Huffington Post that she would vote against second reading. However she added that she would not resign and would force David Cameron to sack her.
Earlier on Tuesday the government admitted it could no longer dictate the timetable of the Lords Reform Bill and abandoned a programme motion vote scheduled for later on Tuesday night.. It was an acknowledgement that it faced a massive rebellion from Tory MPs who opposed major constitutional changes being given only 10 days of debate on the floor of the Commons.
Leader of the House of Commons Sir George Young has confirmed the government has ditched the "programme motion" which would have set the number of days MPs would spend discussing Nick Clegg's plan to introduce a largely-elected House of Lords.
The U-turn means the Bill on Lords reform is now in limbo until at least September, and the onus is on David Cameron to try to win rebel Tories around over the summer.
Sir George Young told MPs: "We have listened carefully to the debate so far, confident that we will get a significant majority at second reading tonight.
"But for Lords reform to progress it needs those that support reform to vote for reform and to vote for that reform to make progress through this House.
"It is clear that the Opposition are not prepared to do that, so we will not move the programme motion tonight."
Sources close to the deputy prime minister laid the blame for the abandoning of the timetable at the feet of both the Labour Party and Tory rebels. "It is a plague on both their houses," they said.
And the source insisted that the Lib Dems had not been hurt by the row. "I don't actually think we've sustained any damage," they said.
The Bill will now proceed to a committee of the whole House, where it is likely to still face filibustering from Tories who oppose in principle the vision for an elected House of Lords.
The decision means Labour can no longer use a vote against a programme motion to inconvenience the government, but it still means a vast amount of House of Commons time will be spent discussing Lords reform in the autumn.
There is speculation that the government will now attempt to do a deal with Labour to try to agree on a number of days the Bill will be discussed.
Labour will come under pressure to agree a reasonable number of days, more than the 10 originally offered by the government.
Labour maintain that Nick Clegg's bill is flawed, and could still vote against parts or all of the Bill at a later stage, giving Tory rebels another chance to scupper the reforms.