Vaz adds his voice to the clamour for an EU ballot

Former Europe minister Keith Vaz fuelled the campaign to give the public a say on the revived EU constitution by calling on the Premier to hold a poll on the same day as a general election.

Although Mr Vaz backs the constitution, his suggestion was seized with glee by referendum campaigners, who claimed it showed the Government is wavering.

Mr Brown has rejected calls for a referendum, insisting it should be up to Parliament to approve the new EU treaty.

But critics claim he is riding roughshod over Labour's manifesto pledge at the last election to give voters a say.

The original constitution was killed off by voters in France and Holland in 2005.

Campaigners claim the new draft reform treaty, agreed by EU leaders in June, is almost identical and should also be put to a referendum.

Shadow Foreign Secretary William Hague claimed last night that the Government's case for not holding a vote was collapsing.

He said: "Keith Vaz is absolutely right. More and more veteran Labour figures are coming forward to demand that Labour's manifesto promise is kept. Mr Brown's misjudged position is becoming badly exposed."

Mr Vaz wants the referendum to ask a wider question: "Do you support Britain's continuing membership of the EU as set out under the terms of the Reform Treaty?"

He accused opponents of the treaty of wanting to end Britain's membership of the EU, and said a referendum would force them to "put up or shut up".

Writing in the Labour-supporting Sun newspaper, he said: 'Gordon Brown has made a terrific start to his premiership. He is trusted by the public.

"It is time for the Government to trust the people on this issue. We have nothing to fear."

Former minister Graham Stringer welcomed the intervention and said the campaign for a referendum was "gathering momentum".

The MP for Manchester Blackley said a majority of all 659 MPs wanted a referendum.

With more than 100 Labour MPs reported to be in favour, along with all 197 Tories and dozens from smaller parties, Mr Brown could face defeat if the Commons votes on the issue.

Mr Stringer admitted a defeat would create problems for the Prime Minister, but insisted: "It will be much more damaging not to hold a referendum than to hold a referendum and lose it."