Conservative leader Iain Duncan Smith has launched what he calls a "big fight back" against the growth of a European super state.
Iain Duncan Smith made his name as a Maastricht rebel
Mr Duncan Smith, in Prague for his first major speech about Europe as party leader, also tried to scotch Labour claims that the Tories want Britain to pull out of the EU altogether.
Again calling for a referendum on the draft EU constitution, Mr Duncan Smith said he wanted a Europe of democracies rather than a United States of Europe.
His comments "dismayed" former Tory chancellor Ken Clarke, who said Mr Duncan Smith "shouldn't pretend the speech isn't a call for a withdrawal from the European Union in any recognisable form".
'No withdrawal plan'
Ahead of the speech, Mr Duncan Smith told BBC News: "We are beginning the fight back.
"We want the EU to be about nations democratically elected and governing in an outward looking Europe, not this centralised super state."
Labour leaders say the Conservatives want Britain to be a "semi-detached" EU member, a suggestion Mr Duncan Smith moved to deny in his speech.
He said: "The Conservative Party does not want Britain to leave the European Union.
We want to make it work.
"Anyone who says differently is telling a lie.
"The truth is that we are as committed to building a New Europe of sovereign democracies as we are opposed to a United States of Europe."
Mr Duncan Smith, who made his name by rebelling against the Maastricht Treaty, lambasted "old Europe" as he outlined how he would like Europe to be.
"This is our vision: a Europe of national democracies, trading freely with each other and committed to freedom and democracy around the world," he said.
"There are those who wilfully misrepresent the choices facing Europe's democracies.
"They are trying to bully the British and Europe's other peoples into believing that it's Old Europe or no Europe.
Clarke says Duncan Smith's approach will not extend Tory support
"Old Europe has closed its mind to the possibilities of New Europe.
"It says all Europe's nations must accept the euro, accept the constitution, accept the aid budget riddled with corruption, accept the common foreign policy, accept the common defence policy, accept all these things or they must get out."
Instead, countries had every right to be in the EU and reject the euro and the constitution, he argued.
"Some claim the British people will lose influence if they reject Old Europe's agenda," said Mr Duncan Smith.
"But influence must never be bought at the price of our permanent interest."
The Tory leader renewed his calls for a referendum over the draft EU constitution, which he said would stop individual countries changing the highest laws which governed them.
Mr Duncan Smith continued: "There is no hiding what stares us in the face:
a constitution that would lead inescapably to ever more power being transferred to Brussels,
a blueprint for a United States of Europe in all but name."
The prime minister has rejected calls for a referendum, insisting the proposed constitution would not fundamentally change Britain's position within the EU.
That view was backed by ex-Tory leadership challenger Mr Clarke who, in an intervention likely to anger his party's leader, said "it was no good raising the bogeyman of an EU super state".
It was "absurd" to talk of EU law overriding British law as those
arguments had already been fought and conceded more than 30 years
ago, said Mr Clarke.
He added: "The party that was in government, the party that used to win elections did not have these opinions.
"It was opinions of this kind that made Iain Duncan Smith such an isolated rebel."
In Thursday's Commons debate on the euro, Chancellor Gordon Brown accused the Conservatives of being against EU membership.
They wanted Britain to veto the
inter-governmental conference which will decide the final version of the EU constitution so Europe was put into crisis.
"They then move to a situation where they have semi-detached membership of the
European Union, associate membership or some other relationship," added Mr Brown.