NO 10 has played down suggestions that David Cameron's EU renegotiation has already suffered a major setback before it has barely begun.

It has been suggested France and Germany have struck a private deal to integrate the core eurozone group more closely but without the need for fundamental treaty change.

The Prime Minister's spokesman confirmed Mr Cameron still believed opening up EU treaties would be needed to secure the welfare and other reforms he is demanding.

But the spokesman argued any revisions to eurozone rules were not inextricably linked to the changes the Conservative Government wanted.

"There are a distinct set of issues that deal with the changes that are required in the eurozone...and a wider set of issues, which are the issues which the Prime Minister has referred to," he explained.

Mr Cameron is due to embark on a whistle-stop tour of European capitals later this week as he "gets down to business" with the renegotiation.

Tomorrow, he will visit Denmark and the Netherlands, ending the day dining with President Francois Hollande in the Elysee Palace.

Then on Friday, after a meeting in Warsaw, he will travel to Berlin for lunch with German Chancellor Angela Merkel.

Downing Street made clear other visits to EU leaders was possible ahead of the Brussels summit in late June.

In weekend talks at Chequers with European Commission President Jean-Claude Juncker, the PM warned the EU "needs to change" to meet UK voters' concerns. Mr Juncker repeated his desire to find a "fair deal" for Britain.

Primary among today's measures in the UK Government's legislative programme will be the EU Referendum Bill, which will set out the procedures for holding the in/out poll before the end of 2017.

Liam Fox, the former Defence Secretary, who is a leading Eurosceptic, cautioned his Tory colleague from seeking to go early and hold the referendum next year.

Some senior Conservatives like Ken Clarke, the former Chancellor, and Boris Johnson, the London Mayor, have called for an early vote. Labour's Andy Burnham, the frontrunner in the party's leadership race, and Nigel Farage, the Ukip leader, have also called for the in/out poll to be brought forward.

But Dr Fox questioned the motives of those demanding an earlier vote.

"Those who are urging him to go for a referendum in 2016 have ulterior motives, which are not entirely honourable," claimed the former Glasgow GP, who represents a Somerset seat.

"They want to see a decision made quickly to limit the level of debate in the United Kingdom; they are afraid that if we have a very full debate, then some of the real unacceptable issues in Europe at the present time will become all the more clearly seen by the British public.

"We need a proper grown-up debate; it's the most important constitutional issue of my lifetime. No one under 58 has had a say on this in our country; it's something that we should properly take our time over," he added.