Image caption David Cameron has said a lot can be achieved without any treaty changes

No 10 has said none of the proposed changes being discussed about the future shape of the European Union would trigger a referendum in the UK.

Germany and France are developing a plan for greater fiscal integration among the eurozone's 17 members ahead of a crucial meeting on Friday.

Many MPs say this would alter relations with the EU and a referendum is needed.

But Downing Street said it did not meet the test for a vote, which required a major transfer of powers to Brussels.

German Chancellor Angela Merkel and French President Nicolas Sarkozy met on Monday to discuss a blueprint for the future shape of the eurozone, as well as urgent steps to deal with Europe's financial and economic problems.

'Not on table'

The meeting came ahead of a summit of all 27 EU leaders on Friday seen as crucial to supporting the euro and signalling the future direction of the eurozone.

Following the meeting between their two leaders, Germany and France said the EU needed a new treaty signed by all EU members, but if that was not possible, signed by the 17 states which have adopted the euro.

While the UK is not a member of the single currency, the prime minister says he will defend the UK's national interests should the eurozone move towards closer fiscal union and budgetary co-operation.

But he is likely to face renewed calls for a referendum on any changes in the UK.

Last month, more than 80 Tory MPs defied the government and called for a referendum on the UK's membership of the EU.

One of them, the leading Tory eurosceptic Bill Cash says in the light of the call for a new treaty there must now be a referendum.

"This is a major Treaty change whether it is for the eurozone-17 or the EU-27 because it fundamentally changes the relationship of Britain to the EU," he says.

"It therefore requires a referendum, irrespective of the attempt to bypass the British people with the European Union Act this year."

The former Tory Cabinet minister John Redwood said a referendum would strengthen David Cameron's hand in future EU talks.

"What a lot of us are advising him is that this is an opportunity now to redefine Britain's relationship," he said. "The best sanction to try and get something in Britain that we want is to say that any treaty change will have to be approved by the British people."

The coalition has said there will only be a referendum if there is a further substantial transfer of powers from Westminster to Brussels.

But there has been tension between the Conservatives and Lib Dem partners over what would trigger this.

"Referendum lock"

Deputy Prime Minister Nick Clegg said on Sunday that a public vote was unlikely because the eurozone changes could be secured without a treaty change, but Work and Pensions Secretary Iain Duncan Smith said the public must be consulted in the event of any major treaty change.

But No 10 indicated on Monday that a referendum was unlikely under the terms of the "referendum lock" legislation passed by Parliament last year.

And Mr Cameron said, after an NHS speech: "As prime minister, I am not intending to pass any powers from Britain to Brussels. So I don't think the issue will arise.

The measures under consideration were about how the eurozone countries organised and governed themselves, Downing Street added.

Conor Burns, parliamentary private secretary to the Northern Ireland Secretary Owen Paterson, said MPs in government and on the backbenches were urging the prime minister to fulfil the party's election pledge to repatriate powers.

"We should use the opportunity of this treaty change to say to our European partners: 'If you want to go down the route you are going down, please carry on,'" he told BBC Radio 4's World at One programme. "But this is the opportunity, finally, to get the British dog out of the federalist manger."

Financial veto

Some MPs are backing a proposal from the Open Europe think-tank for a veto on financial regulation coming out of Brussels which might damage the City of London.

In a new report, Open Europe warns that the UK is increasingly losing influence over financial regulation coming out of Brussels, often finding itself outvoted, and that the UK must fight its own corner as the eurozone "pushes its own agenda".

"There is a growing divergence between the UK's economic interests and the slew of regulations coming from Europe," said its director, Mats Persson.

The Labour leader Ed Miliband says Mr Cameron is not at the heart of the debate on Europe's future as he should be.

"What I actually see is a Prime Minister who is standing on the sidelines or having a row within his own party about what needs to happen in Europe," he said.