Calls from France and Germany for a new European referendum have reignited tensions over the EU within the Conservative party.
Following crisis talks in Paris, French President Nicolas Sarkozy and German Chancellor Angela Merkel said that eurozone states should face sanctions for running up large deficits.
The pair called for the 27 countries of the EU to move towards greater fiscal integration to ensure the current financial crisis is not repeated. If that was not possible, just the 17 states that have adopted the euro should move forward, they said.
"Whatever has happened must never happen again, and it's for this reason we want a new treaty," said Sarkozy. "This is what Germany and France want."
Prime minister David Cameron said he did not believe a new Treaty would pass power from UK to Brussels, thus triggering a referendum.
Answering questions after a speech on Monday, he said: "Clearly, there are negotiations going on in Europe. I will be part of those negotiations on Thursday and Friday. If there is a Treaty at the level of 27, and if that passed powers from Britain to Brussels, there would be a referendum."
A Downing Street spokesman said on Monday afternoon any such change would lead to a public vote.
"I don't think there was anything in what they were proposing that would imply any transfer of powers from the UK, from Westminster, to Brussels. And the Prime Minister just set out our position on that, and he was very clear when he was asked about this row ten minutes ago that he wouldn't allow anything that would imply a transfer of powers from Westminster to Brussels."
But Conservative backbenchers have already raised concerns about the proposed new EU treaty.
Tory MP Bill Cash told the BBC the call for a new arrangement was "like giving a heroin addict more heroin" and that Britons "must have their say".
And Downing Street earlier slapped down suggestions from work and pensions secretary Iain Duncan Smith that any treaty changes would lead to a referendum under the European Union Act.
While markets rallied following Merkel and Sarkozy's announcement, it was followed by reports in the Financial Times that ratings agency Standard and Poors planned to put AAA-rated eurozone governments, including Germany, on "creditwatch negative".