Another Conservative ministerial aide has said she will defy the Government whips and vote against Nick Clegg's plans for House of Lords reform in tonight's crunch vote.
Angie Bray - parliamentary private secretary (PPS) to Cabinet Office Minister Francis Maude - said she would oppose both the Bill itself and a vital timetable motion, event though it could cost her her job.
"I guess that in normal circumstances those who don't stand by the Government line get the chop so I'll wait for them to do that if that's what they want to do," she told BBC Radio 4's The World at One.
"But I don't feel that I need to resign because I don't actually feel that I'm doing anything wrong and certainly I'm not in any way going against what our own Conservative manifesto laid out."
One ministerial aide - Conor Burns, the PPS to Northern Ireland Secretary Owen Paterson, has already informed the whips that he intends to vote against the Bill in the division tonight in the House of Commons.
With about 70 Tory MPs having come out in opposition to the reform proposals, there was speculation at Westminster that ministers may decide not to put the timetable motion to a vote in order to avoid a potentially damaging defeat.
The timetable motion, which allows ministers to limit the time for debate in the Commons, is seen as essential if the Bill is not to be "talked out" by opponents making marathon speeches.
Although Labour supports Lords reform in principle, it has said it will vote against the timetable - arguing ministers have not allowed sufficient time to scrutinise such an important constitutional measure - raising the real prospect of a Government defeat if the vote goes ahead.
Defeat for the Government would be a bitter blow for the Liberal Democrats who have staked their hopes of achieving major constitutional reform on the Bill after their defeat in the referendum on AV voting in parliamentary elections.
However Ms Bray said they would only have themselves to blame after the Lib Dems threatened to derail plans to redraw the parliamentary boundaries - which experts say could be worth 20 extra seats to the Tories at the next election - if they did not get their way.
"In many ways the Liberal Democrats themselves have been responsible for where we are now. They have played their hand in my view very badly," she said.
"To come out with all these threats - not supporting us on further constitutional change in the House of Commons - has just been red-rag-to-a-bull type stuff and I think they have made a big mistake on that,"
Earlier, Foreign Secretary William Hague acknowledged that tonight's votes would be a big test for the coalition.
He denied reports that he had been approaching Tory rebels with "a twinkle in his eye", implying that they need not vote for the legislation.
"I often have a twinkle in my eye but I don't go round telling people, implying, that they should not do what I am asking them to do," he told the BBC Radio 4 Today programme.
"So I am saying to my colleagues, make no mistake about it, they should vote for it and they should vote for all the government motions in Parliament."
At the same, however, Mr Hague said he recognised that some of his colleagues were opposed to the plans.
"That's a perfectly honourable opinion," he said.
He accused Labour of "opposition for opposition's sake" in its decision to vote against the timetable motion despite support the reforms.
"We are not going to get a better and more sensible package of reform than this one," he said.
"There is strong support for this in all of the political parties so if all of the people who are in favour of it, and dealing with it after 100 years, do actually vote for it and for a sensible timetable for discussing it then it would get through.
"This is something supported by most of the Liberal Democrat Party and the bulk of the Conservative Party and huge numbers of people in principle in the Labour Party."