So when could there be a referendum on the euro? And when could the UK join the euro if the British people gave the idea the green light? BBC News Online's Mark Davies assesses the possible timetable.
Autumn 2003: Not a hope. One of the very few concrete things to come out of Mr Brown's statement is that there won't be a referendum on the euro this year.
Spring 2004: Forget it. Mr Brown said he will return to the euro question in his Budget early next year. And even then he'll only be saying whether he thinks it's worth assessing the case for the currency again.
And even if he did that overnight, there still has to be a four month gap between a positive assessment and a referendum.
Autumn 2004: A distant possibility. If the chancellor was to (a) say in his Budget that he'll be reassessing the case for the euro and (b) did it quickly, there could be a poll four months later towards the end of 2004.
A "yes" vote then would mean euro notes and coins in the UK in 2007.
The advantages for the government would be that it leaves a gap between the referendum and the next general election.
But although the idea is being floated by
some at Westminster, most think it is unrealistic.
Spring 2005: A better bet. If Mr Brown decided that the economic conditions were right for euro entry late next year, the government could call a referendum for early in 2005. That would mean euro entry - if the vote was won - in 2007.
But by this stage, a general election - which must be held by summer 2006 - is looming (or could be in the offing).
The government would have to be pretty convinced it could win a euro poll before embarking on such a move so close to a general election.
Losing a referendum would hardly be a good way to go into a national poll.
Autumn 2005: Ditto. By this stage the government would be running things right up to the wire in terms of the next general election (if such a poll hadn't already been held).
There would have to have been significant movement in opinion polls for the government to take a risk on a poll at this stage.
Euro entry under this scenario - again assuming the government won a referendum - slips to 2008.
Spring 2006: This could only really happen if the government had by this stage already been returned to power in a general election in 2005.
Otherwise it would be way too close to the final possible dates for a general election. And a referendum on the euro couldn't be held on the same day as a general election.
A "yes" vote now could lead to euro notes and coins in the UK in 2008.
Autumn 2006: The ifs and buts become almost impenetrable by now.
If there'd been a general election in 2005 or early 2006 - and if Labour had been returned to power - this date is possible.
Labour might have made a euro referendum - a chance to rule on the issue once and for all - part of its manifesto. For the incoming government it would at least get the issue sorted once and for all.
Euro membership under this scenario would be in 2009.
Spring 2007: If Labour wins the next election, this could be the time to call the poll. Most commentators don't expect a referendum until now at least. And that relies on Labour being able to win the general election.
Euro notes and coins in the UK would be as far away as 2009.