Tony Blair has pledged not to "hold back" from calling a referendum on the single currency for political reasons.

What I'm saying is if the tests are passed we should do it Tony Blair

In an interview with BBC Radio 4's Today programme, the prime minister said he believed "passionately" it was the UK's "destiny" to be at the centre of Europe.

But, he added, the country should only sign up to monetary union if it was right for the economy and the Treasury's five tests had been met.

Critics have accused Mr Blair of using the five tests as an excuse to delay a vote until the opinion polls are more favourable.

'Right for economy'

Pro-euro campaigners are worried the government will be forced to put a referendum on the back burner because of events in the Middle East and domestic issues such as the row over private finance in the public sector.

In his keynote Labour conference speech on Tuesday, Mr Blair attempted to dispel such doubts by pledging to "go for" a referendum, if the Treasury's tests are met.

But in Thursday's Today interview, he sounded a more cautious note.

"What I'm really saying to people is don't hold back for political reasons," he told the programme.

"I think it is important for Britain to be a central and leading player in Europe.

"However, we can't do the euro unless it is right for the British economy."

No talk of dates

The Treasury has pledged to complete the five economic tests by next June.

Asked if that meant he would hold a referendum in the Autumn, Mr Blair said: "I am not getting into the dates of any potential referendum.

"What I'm saying is if the tests are passed we should do it."

The five tests assess whether the UK economy is in step with the eurozone and the impact of euro entry on the City, jobs, economic flexibility and investment.

'Important arguments'

Mr Blair said it was time the UK "made the most" of being in Europe.

"Let's have confidence in the fact that Britain can be a key and leading player in Europe," he told Today.

"There are huge arguments going on in Europe at the moment of vital, fundamental importance to the future of this country.

"Abut economic reform about the enlargement of Europe, the institutions of Europe, about how the single currency works about how foreign policy and defence policy work.

"For Britain, it is essential that those arguments are resolved in the right way for this country."

But, equally, he said he would not want to leave office if he had "tried to take the country into the euro in the wrong economic circumstances".

In his conference speech, Mr Blair urged Europe to have the "courage" to tackle economic reform.