Jack Straw said the constitution was good for Britain

Foreign Secretary Jack Straw used an article in the Times to attack the Tories for their opposition to the proposals.

And Chancellor Gordon Brown wrote in the Wall Street Journal of his belief that Britain was getting its own way under the plans.

The Conservatives are demanding a referendum on the draft constitution, which was published this week by the convention on Europe's future.

They have warned the constitution is a "step change" towards a federal Europe with the UK losing sovereignty over many policy areas.

DRAFT PROPOSALS Powerful EU president EU foreign minister Common foreign policy Legally-binding charter of rights EU to have "legal personality" Have your say on referendum Excerpts: EU draft constitution Plans explained point-by-point

But Mr Straw accused the Conservatives of wanting to roll back existing EU powers, renegotiate old treaties and make the UK a second-class member of the EU.

He said: "Many of those leading the campaign against the draft treaty proposals are exactly those who believe the 1992 Maastricht treaty also meant the end of Britain as a sovereign nation.

"They don't seem to have noticed their fears have proved to be mistaken."

He said the draft "does not significantly change the relationship between the EU and its member sovereign nations".

Mr Straw the constitution offered a great chance for Britain to play a "full and leading role" in the EU.

Tory warning

The Tories insist they do not want to leave the EU but their representative on the convention, David Heathcoat-Amory, described the negotiating process as a "dialogue of death"

The MP said there was virtually no chance of altering the draft constitution to meet Tory concerns.

This new draft rule book... does not significantly change the relationship between the EU and its member sovereign nations Jack Straw

Instead, he is asking convention chairman Valery Giscard d'Estaing to let him and other Eurosceptics to produce their own draft.

Meanwhile, Gordon Brown insisted Britain was winning the arguments with its EU partners, on for instance harmonised tax rates - ruled out because of British opposition.

"Federalist ambitions are giving way to inter-governmental realities," he said.

The chancellor said he believed a pro-European consensus could be built in Britain, if the electorate could be convinced of its merits.

The draft constitution proposes an elected EU president and foreign minister, and backs a common foreign policy.

There are also plans to replace in some policy areas the system where all EU countries must agree on a decision, in favour of majority voting.

'No rights change'

The government promised on Tuesday to block some items, including plans to make an existing charter of worker's rights legally binding.

It also came out against plans for a "European Public Prosecutor" for serious crimes.

On Wednesday, outgoing TUC general secretary John Monks tried to quell fears about the workers rights' proposals.

"We wish it was going to give us more rights than we have got at the moment," he told BBC Radio 4's Today programme.

"But actually we do not think it is a major step forward in that respect."

Wales Secretary Peter Hain, the UK government representative on the convention, has rejected calls for a referendum on the plans.

EUROPEAN CONVENTION Chaired by Valery Giscard d'Estaing Holding year-long discussions Aims to simplify treaties Trying to decide balance of power between Brussels and governments More about the convention

Mr Hain prompted a row on Tuesday when he said that if people did not like the new constitution, they could vote against the government at next year's European elections.

He later dismissed as "absurd" suggestions that he was suggesting the European polls would become a de facto referendum on the plans.

The proposals are aimed at setting out a vision of how the EU will be run after 10 new countries join next year.

References to a "federal" Europe were dropped at UK Prime Minister Tony Blair's request. Calls to rename the EU as "United Europe" have also been rejected amid UK concern.

The draft will be debated by the convention this week and then considered by EU leaders at a summit in Greece in June.