Tony Blair has accused the Conservative leader of conspiring to take Britain out of the European Union.

Writing in Thursday's Mirror newspaper, the prime minister said his opposite number makes Margaret Thatcher "look like a euro-fanatic" in comparison.

While the former party leader "knew Britain's future was in Europe", Blair argued, "it is becoming crystal clear that Iain Duncan Smith and the modern Tory party want us out".

He wrote that the Conservative policy on "re-negotiation" of major European treaties and opposing the Convention on the Future of Europe's draft constitution is a ploy to bring Britain out of the EU.

"We all know you can't stay in any club if you say you will ignore most of the existing rules," he said.

Withdrawal - which Duncan Smith denies is his aim - would be a "national disaster" for British jobs, security and environment, Blair said.

And he drew on the words of another of Duncan Smith's predecessors who said that there was no option of re-negotiation on the table.

"It was John Major who said re-negotiation is just code for withdrawal from Europe," Blair claimed.

On the day he set off for a summit of EU leaders in Greece to discuss the Convention's proposals, the prime minister conceded that Britain could not have everything its own way.

"Sometimes, of course, progress is slower than you would like," he admitted.

"But the way you win in Europe is by being committed and helping shape its future direction - as we are doing...not by walking away."

Shadow foreign secretary Michael Ancram said that the prime minister had deliberately misrepresented his party's views."This is another step in the government's attempt to create a false debate about Europe," he said.

"They are determined to try to make this debate a question of 'staying in' or 'coming out'.

"They are doing this because they know that the real debate about what sort of Europe we should be seeking is one they cannot win because they have sold out to those who wish to build a European superstate."