David Cameron is facing increasing pressure from his own backbenchers as he heads to a make-or-break European summit in Brussels.
Downing Street insisted on Thursday morning that the prime minister was "focused on securing the best deal for Britain" at the summit, which concludes on Friday. But by the afternoon he was compared to Neville Chamberlain by eurosceptic backbench MP Edward Leigh.
Nicolas Sarkozy and Angela Merkel are expected to call for measures prohibiting eurozone countries from accruing too much debt, and a eurozone rulebook to encourage greater fiscal integration.
Their plans come as European Commissioner Jose Manuel Barroso urged European leaders to "do everything" to save the euro, saying: "The world awaits not more national problems but European solutions."
Cameron faces a challenge from his own European counterparts, with German chancellor Merkel suggesting she will reject his demands to protect Britain's interests, saying the key is saving the eurozone.
But backbench Conservatives have also urged the government to use the summit as an opportunity to repatriate powers back from the European Union.
Former leadership candidate David Davis said on Thursday morning: "The raw politics of this is that if there is a significant change in the balance of power in Europe - that's the test. If there's a significant change in the balance of power, it has big implications for our future, that's the point at which you have to have a referendum."
And top Tories including Cabinet minister Owen Paterson and Mayor of London Boris Johnson said a referendum on the UK's position in Europe would be inevitable if this week's meeting led to treaty changes.
Despite this Cameron has promised to bring the "British bulldog" spirit to Brussels. Speaking ahead of his trip, he said Britain needed the european market but acknowledged "the euro, the single currency, isn't working properly".
"That's having a terrible effect on those countries, but it's also having a big impact on us, and we need those eurozone countries to come together, to make changes, to sort out their problems, and to get the institutions of the eurozone behind that currency, so they get their economies moving again, and that'll be good for us", he said on Thursday morning.
Chancellor George Osborne has also vowed to protect the interests of states that were not in the eurozone, to avoid a two-tier Europe.
"You’re right to point to the risk of caucusing," he told the Lords on Thursday.
"There was a concern about caucusing when the euro was created. If anything there probably hasn’t been enough coordination in the euro zone. That’s why we’re seeking protections for the 27 members of the EU," he said.
On Wednesday evening, Standard and Poor's put the EU's AAA credit rating on negative watch.
The politics of dissent: What key figures are saying about the eurozone
The former Tory leadership candidate: "The Government wrote that bill very narrowly - they were criticised for it - but it's not as narrow as they think. But secondly, the raw politics of this is that if there is a significant change in the balance of power in Europe - that's the test. If there's a significant change in the balance of power, it has big implications for our future, that's the point at which you have to have a referendum."
Jenkin, a Conservative backbencher, claims: "The only reason they want it is so they can tax the City of London. We've got to get out from under those sorts of arrangements, and that means changing the relationship we have with the European Union. And the difficulty we've got now is that the eurozone states, there's 17 of them, and if they're allowed to create this economic bloc with this new treaty, they're going to outvote us on everything. "It's going to be a completely different European Union. There are going to be two Europes; there's going to be the eurozone Europe, and there's going to be countries like Britain which are just satellites on the outside that are just dragged along in the slipstream. "You're going to hear Michael Fallon say this has no effect on the United Kingdom, no legal effect. Well that's real dancing angels on a pinhead. It's going to have a massive effect on our relationship, this big change in European, and therefore we're entitled to ask for a change, and if we don't get that change, then we're entitled to say this should be put to the British people, and then the British people can vote no so we can get a better deal."
Said the Conservative member for Sevenoaks: "We don't yet know whether the changes that are being proposed would fundamentally alter the nature of the European Union. If they want to use the institutions of the European Union, if they want to use European law for any new bloc, then of course we can demand safeguards, because we would have to agree to that, but that's not yet been put on the table."
The former Tory leader said: "What is pressing at the moment as we sit here today, is the need to help the eurozone overcome its crisis, because the world economy is in a very fragile state and a disorderly break-up of the eurozone could bring about an economic catastrophe on a global scale. "Why do you think the American Treasury Secretary has been visiting Europe so frequently over the last few months? So the challenge facing the Prime Minister today and tomorrow is to help the eurozone to overcome that crisis while of course making sure - and I'm sure that he will do this - that Britain's interests are safeguarded."
The former leader of the Liberal Democrats said: "I personally feel that a referendum is now pretty well inevitable because of the position that Mr Cameron has got himself into... I was the first person to coin the phrase if we're going to pass more power to Europe we cannot do it unless you consult the British people on the referendum. If that's what's going to happen then there has to be a referendum."
"The Prime Minister has been quite clear, and this is something that we all share in this Coalition Government, I mean I work in lockstep, hand in glove, with the Prime Minister on these issues, and as we are supportive to the Eurozone so they can sort their problems out, in return they introduce safeguards to ensure precisely what I said: that the single market is not fragmented and that important industries like the financial services industry are treated fairly. Not exceptional treatment, but are just simply treated fairly, on a level playing field within Europe."
"The basic falsity of the whole thing is that its nonsense. As we argued at the time of the Maastricht Treaty to think that you can have a single a interest rate for a whole variety of countries at different stages in their development."