The prime minister has rejected Iain Duncan Smith's call for a referendum on any new European Union constitution.

Speaking in the Commons, Tony Blair said there would be no significant concessions in the key areas of foreign and defence cooperation.

But the Conservative leader said the government was denying the British people a chance to express their views.

Duncan Smith said there had been 34 referendums since Labour came to power.

"Why won't the prime minister simply let the British people have their say?" he asked.

But Blair rejected "scaremongering" about the implications of the discussions underway at the Convention on the Future of Europe.

"I see no case for having a referendum on this," he said.

And Blair accused Duncan Smith of wanting a referendum because "under his leadership the Conservative Party remains utterly and implacably opposed to Europe".

The Conservative leader said that he simply wanted to give the British people "the right to say no".

Echoing Clare Short's criticisms of the prime minister, Duncan Smith said that failing to hold a referendum would prove that the prime minister was out of touch and arrogant.

But Blair said the Conservatives were in effect rejecting European enlargement because they opposed the reforms necessary to allow an EU of 25 member states to work effectively.

"What we now know from this Conservative Party is that they are against the enlargement of the European Union...under his leadership the Conservative Party are against Europe which is a disaster for jobs and this country."

He said the Tories were not just opposed to the single currency "but the accession by the 10 new member states".