David Cameron is facing renewed backbench disquiet over the European Union after he tried and failed to satisfy Conservative demands for a referendum.

Conservative MPs warned that the Prime Minister had not gone far enough by declaring that he would consider calling a referendum - but not yet.

Mr Cameron was accused of offering "jam tomorrow" with his offer to go to the people once Britain's future relationship with Brussels, in the aftermath of the eurozone crisis and further EU integration, becomes clear.

He insisted that an immediate in/out referendum was not what the public wanted, but, in an article for The Sunday Telegraph, Mr Cameron acknowledged the need to ensure the UK's position within an evolving EU has "the full-hearted support of the British people".

He stressed there would be further opportunities in the coming months and years to win back powers from Brussels and that he wanted to be able to offer voters a "real choice" in any potential referendum. "As I have said, for me the two words 'Europe' and 'referendum' can go together, particularly if we really are proposing a change in how our country is governed, but let us get the people a real choice first."

He is expected to set out more detail about the possibility of a referendum in the autumn. But influential eurosceptic backbencher Mark Pritchard said Tory grassroots were "fed up of aluminium guarantees" and insisted there should be a referendum during the current parliament. "Once again, when it comes to Europe, it's always jam tomorrow. But tomorrow may never come," he said.

Nearly 100 Conservative MPs wrote to Mr Cameron recently urging him to make a legal commitment to hold a poll on the UK's relationship with the EU during the next parliament.

The issue also threatens to place new strains on the Tory coalition with the Liberal Democrats, who said Mr Cameron was not speaking for the Government and suggested he was responding to "internal divisions" in his party.

Lib Dem Business Secretary Vince Cable said the referendum question was "horribly irrelevant", adding: "Reopening a big debate about Britain being in or out of the European Union and the referendum associated with it is horribly irrelevant at a time of upheaval taking place in Europe."

Labour said Mr Cameron's positioning on a referendum was a "shambles" and revealed more about his "weakness" in managing his party than in his plans for a plebiscite.