The head of the Electoral Commission has warned ministers he will not shrink from speaking if the words they choose for a euro referendum are unfair.

The government has to consult the commission on the wording of any referendum question and Sam Younger said he would not be bounced into accepting their proposal.

The commission is there to give an independent view and an independent view we will give

Sam Younger Electoral Commission

Eurosceptics have claimed the question could be rigged and Mr Younger has already refused to vet the wording before it is published and debated by political parties.

The new comments come after Chancellor Gordon Brown this week gave more details of his economic tests for euro entry, which the government says have to be met before any referendum.

Advice role

That test will be completed by June next year, although many observers have predicted Mr Blair could opt for a euro vote next spring.

By law, the government has to consult the Electoral Commission over the referendum question but it does not have to heed that advice.

The prime minister, however, has said he cannot imagine politicians ignoring an independent commission if it said it did not like the question.

Blair has suggested having one simple question

Mr Younger told BBC Radio 4's Today programme: "I am sure it would be the case that government in bringing in legislation on any referendum would not want the question to be one the Electoral Commission rubbished as being unfair.

"They would not want to be in that position and I would hope that it does not get to that position."

The commission had an obligation to make sure any referendum question was "intelligible and fair" without "fear or favour", said Mr Younger.

He was sure the commission would come under "enormous pressure" if it said criticised the wording.

Question under question

"But in positive terms, the commission is there to give an independent view and an independent view we will give," added Mr Younger.

The prime minister has suggested the question should be simple, something like: "Do you want to join a single currency or not?"

BBC political correspondent Norman Smith says the Electoral Commission's thinking is rather different.

It is understood to be against using a "yes or no" question as the word "yes" could encourage people to vote in a positive way.

Instead, there could be two propositions asking people whether they either want to join a single currency or whether they want to retain sterling.

Campaign leaders?

Close scrutiny of the language is under way, examining whether "join" might be too inclusive a word to use, encouraging voting in a particular way.

The commission will publish guidance on what wording might be appropriate ahead of any referendum.

Conservative foreign affairs spokesman Michael Ancram said he welcomed Mr Younger's comments.

"We hope he will use all powers available to him to ensure that any question put will be scrupulously fair to both sides of the argument.

"However, we will wait to see if Tony Blair has the courage of his convictions and calls a referendum.

"This is certainly a setback to those who thought they could rig a euro referendum."

On Wednesday, Tory leader Iain Duncan Smith said he would be at the forefront of the "no" campaign in a euro vote.

His chief strategist has suggested the Tories would be kept at arms length by the anti-euro campaign, which wants its appeal to be non-political.