A final decision on the euro will be taken in the "national economic interest", Gordon Brown has said insisted.

Refusing to say whether he would keep open the option of rerunning the five tests next year if the criteria are not met, the chancellor said he would not pre-judge the current assessment.

"If the assessment is 'yes' then we will put the matter to parliament and then to people in a referendum," he said.

"If the assessment is 'no' then we will explain the next stage at the time at which we make the decision, we cannot be clearer than that."

The chancellor said the key factor was whether the economic benefits were "clear and unambiguous".

"We are committed in principle but we do have to be absolutely sure that the national economic interest test is met," he said.

Brown also signalled that he will lobby his EU counterparts to allow Britain to continue to display the Queen's head on euro notes should the UK decide to join the single currency.

"My view is that there should be a national symbol," he said.

Amid reports that he is blocking the prime minister's demands for an early referendum, Brown said he was working with Tony Blair to formulate euro policy.

"We talk about these things and we discuss these things. Obviously the prime minister is involved in this process and it is right he should be," he added.

But he dismissed those who said Britain should join the euro come what may.

"I would not agree with those people who say 'let's join and hope we can get the sustainable and durable convergence'," he said.

"We have got to show that we have a settled period of convergence set down there and it is likely to be sustained."

The chancellor dismissed claims that the public apathy towards the single currency could be read as hostility.

"When the issue is joining there is no lack of interest in it," he said. "I have got no about that this [a referendum] would evoke a huge amount of interest."

The probe comes as part of the Treasury affairs committee's inquiry into British membership of the single currency.

Brown, who was last year accused of pulling strings to delay the beginning of the committee's inquiry, has been accused of blowing cold on the euro over recent months.

MPs were seeking an update on the chancellor's five tests, which are set for completion in the next 12 weeks.

They also questioned Brown over the effects of his increased borrowing on Britain's chances of euro membership.

Brussels is said to be concerned that the chancellor's burgeoning budget deficit breaks the strict rules contained within the EU's stability pact.

Brown said he would "not accept the federal approach to economic policy".

The chancellor said he would stand firm against any further attempts to give Brussels control over fiscal policy.

"As far as the centralisation of fiscal policy, I will oppose that," he said.

"I neither think tax harmonisation is necessary to make the single currency work nor do I think it is necessary to move from the inter-governmental basis of the stability and growth pact."

During his appearance before the committee the chancellor also announced that he has ordered a review into the changes that will be required to official statistics and other economic information should Britain join the single currency.

The inquiry is to be headed by Christopher Allsopp, who will soon step down from the Bank of England's monetary policy committee.