Ed Miliband has called for an urgent meeting with David Cameron, Nick Clegg and the chairman of the watchdog responsible for MPs' pay and perks to prevent an "unacceptable" 11% pay rise.
With the Independent Parliamentary Standards Authority (Ipsa) set to publish its recommendations tomorrow, the Labour leader wants the meeting to take place as soon as possible.
In what has been seen as a veiled threat to abolish Ipsa if it presses ahead with the planned rise after the 2015 general election, the Prime Minister said the body needs to think again and "unless they do so, I don't think anyone will want to rule anything out".
Mr Cameron said it was "simply unacceptable" that Ipsa continued to insist on members' salaries increasing by £7,600 to £74,000 after the 2015 general election.
At Prime Minister's Questions he said: "F irst, the idea of an 11% pay rise in one year at a time of pay restraint is simply unacceptable.
"Secondly, Ipsa do need to think again and unless they do so, I don't think anyone will want to rule anything out. No-one wants to go back to MPs voting on their own pay but we have got to have a process and an outcome that can build public confidence.
"Third, in my view, I think this should all be accompanied with a cut in the cost of politics."
The recommended pay rise will be subject to a statutory review by Ipsa after the 2015 contest, and Downing Street said the process should be allowed to run its course.
A No 10 source said: "There's no final decision until 2015. A statutory review is planned after the 2015 election to look at whatever is published tomorrow so probably best to let that process go forward. But I think the PM has been crystal clear what his view is."
Asked if the abolition of Ipsa was a possibility the source said: "He is ruling nothing out."
But the Opposition said the Prime Minister should act now, by taking part in cross-party talks with Ipsa chairman Sir Ian Kennedy.
A senior Labour source said: "That meeting should take place as soon as possible. The three party leaders should jointly make clear this package is unacceptable to the public and cannot go ahead." A lthough Ipsa is an independent body, it should be subject to a "public opinion override" to avert the inflation-busting rise in 2015.
The source said: "The mechanism should be this: Ipsa should listen, Ipsa should think again and Ipsa should realise that we cannot have the package that it is reported to be proposing tomorrow, we cannot have that go ahead when we are having the biggest cost of living crisis in a generation."
The 2015 review process was "not good enough", the source said. "What we can't do is leave this issue hanging around unresolved, what we can't do is let it be delayed until after the 2015 election.
"Ed has made a clear offer to the Prime Minister that we should resolve this and we should resolve this now."
In a letter to Mr Cameron the Labour leader said: "The public expect us to resolve this now and not wait until 2015. It only undermines confidence and trust in our political system if the uncertainty about MPs' pay is allowed to continue.
"Therefore I believe the three party leaders should meet Sir Ian Kennedy tomorrow to make clear our view that we cannot go ahead with the current proposition."