Downing Street has refused to rule out holding a referendum on joining the euro on the same day as a general election.

However a spokesman said the prime minister still stood by a commitment not to.

The government published draft legislation paving the way for a potential poll on Wednesday.

The draft Single European Currency (Referendum) Bill contained clauses which kept open the option of holding a single currency referendum alongside a general election.

A dual ballot would anger eurosceptic campaigners who claim the idea would confuse voters and may help to dupe the electorate into adopting the euro.

Number 10 insisted it was right to retain a range of options despite Tony Blair having previously ruled out combing the referendum with a general election.

"The draft bill gives us maximum flexibility," the official Downing Street spokesman said on Thursday.

"As the prime minister made clear in May, nothing should be read into it regarding the timing of a referendum."

But in further remarks to journalists the spokesman said "it is not going to happen".

"The position has not changed. It is pretty categorical in terms of ruling it out," he claimed.

Blair told reporters in May that: "I have never had the idea of holding a referendum on the same day as the general election."

The government has also revealed the question it would ask the electorate in a euro referendum.

Voters would be asked: "Should the United Kingdom adopt the euro as its currency?".

The phrasing follows guidelines produced by the Electoral Commission.

The bill also confirmed that the question would only be put to the public after both the Cabinet and both Houses of Parliament recommended entry.

Draft legislation was published by the Department for Constitutional Affairs (DCA) to coincide with the chancellor's pre-Budget report to MPs.

Gordon Brown had promised a paving bill before the end of the year in his euro statement in the Commons in June.

The Conservatives accused the government of trying to "bury bad news" under the chancellor's statement.

They also claimed the question was in breach of the Electoral Commission guidelines.

"It makes no mention that the pound would be replaced if people vote 'yes'," constitutional affairs spokesman Alan Duncan said.

"A fair question would make clear the implications for our existing national currency.

"The government are using sleight of hand to hide a euro referendum fix."