Non-British European citizens living in the UK could be able to vote on whether Britain keeps the pound or adopts the euro.
Gordon Brown will examine the case for the euro next year
Ministers have yet to decide whether or not to allow EU citizens to vote in a euro referendum - as they can in local and European elections.
There are more than 725,000 people from other EU countries living in Britain - although government officials suggest only about half of them are registered to vote.
Non-British citizens make up a tiny share of the electorate, but anti-euro MPs say giving them a euro vote would be rigging the referendum.
Chancellor Gordon Brown announced in June that only one of the government's five tests for euro entry had so far been passed.
He will decide in his next Budget whether circumstances have changed enough to justify re-running the tests.
The Financial Times quotes a senior Whitehall insider saying the idea of allowing UK-resident EU citizens to vote in a referendum was "under active consideration".
Ministers could follow the example of general elections, when EU citizens are barred from participating.
A spokeswoman for the Department of Constitutional Affairs told BBC News Online: "The decision has not yet been taken on that. It is something that has yet to be decided."
Giving a referendum vote to EU citizens had not been ruled out, she said.
The department is also considering whether the hundreds of thousands of Britons living abroad, who
have been allowed to take part in general elections and European elections in
the UK since 1985, should also be allowed to vote.
MP Ian Davidson, chairman of Labour Against The Euro, said: "This is the start of attempts to fix the vote.
"I am greatly concerned that the government will try to bias any euro
referendum by manipulating not only the date, but also the rules, the question,
the spending limits and now even the electorate.
"If French, German and Italian people and others wish to vote on the euro
then they should be allowed to do so, but in their own countries.
"A referendum vote in Britain which was influenced by foreign voters would be
Shadow chancellor Michael Howard told the FT: "This is a measure of how desperate the government has become in its attempts to cajole the public into the euro."
James Frayne, campaign manager of the no campaign, told BBC News Online: "With the Eurozone's economy going down the tubes, I wouldn't be surprised if most of them voted no in any referendum. They can see the damage that is being done."
Liberal Democrat foreign affairs spokesman Menzies Campbell said that EU
citizens living in the UK should get a vote.
"These people live here, vote in European and local elections, and contribute
to the prosperity of the UK," he said.
"Why shouldn't they have a vote?"
A spokesman for Britain in Europe said the group had no official view on the question.
He suggested no great principle was at stake as a substantial number of non-British citizens already voted in all elections.
The government is due to publish a "paving" bill in the autumn to put the legislation in place for a referendum in the future.
Pro-euro campaigners see that promise as a "road map" for euro entry, while "no" campaigners dismiss the pledge as a token gesture.
The government has also promised another series of euro road shows to counter anti-European attitudes.
A Treasury spokesman said a number of events had already taken place. The programme would be quieter over the summer, he said.