Tony Blair at the Amsterdam summit

As 12 out of the 15 EU states press ahead with monetary union, one of the biggest questions facing Tony Blair's Labour government is when or even if the UK should take the plunge.

Prime Minister since 1997, Blair has pursued a "prepare and decide" stance, committed in principle to joining the single currency and pledged to hold a referendum on membership when the government believes the time has come to join - a point that will be decided by the chancellor and his "five economic tests".

Britain wants to be one of the three major players in Europe Labour Foreign Secretary Robin Cook

In defeat the Conservatives have hardened their stance on the single currency, at first ruling out membership in at least the medium term, and began campaigning to "save the pound".

By 1999 the strength of anti-European feeling in some quarters was such that it saw the UK Independence Party win seats in the European Parliament for the first time.

The party not only rejected euro membership but was keen to withdraw from the EU itself.

Current Conservative leader Iain Duncan Smith has said he would "never" join the euro.

Key Dates

1997Amsterdam Treaty

1998Central Bank

1999Euro is born

2002Euro in circulation

Labour won re-election in 2001 and Blair has since committed himself to announcing sometime in the first two years of this parliament whether a referendum will be held on membership before the next election.

With such huge question marks hanging over perhaps the biggest political decision of this generation, every possible hint about euro membership is minutely dissected by journalists and analysts.

If they (the five economic tests) are met we should join, and if met in this Parliament we should have the courage of our argument to ask the British people for their consent in this Parliament Tony Blair, 2001

But despite being in favour of the single currency the government is only too aware of the hostility among much of the electorate, and seen in poll after poll, towards scrapping the pound.

If regardless of all his efforts the result of the poll was still No, his own government would be seriously undermined.

Were Tony Blair to decide to hold a referendum on joining the euro, one thing is for certain he would have a massive job turning around British public opinion.