European Central Bank policymaker Yves Mersch called on Tuesday for a single institution to be in charge of the euro zone, adding his voice to ECB pressure to broaden the currency union into more of a fiscal union.

The ECB has used the euro zone debt crisis to gradually push its idea of turning the bloc into something with a central body in charge of its finances and the power to stop debts getting out of control.

On Monday, ECB President Jean-Claude Trichet used his last scheduled public speech to repeat calls for euro zone authorities to have greater powers over the economic policies of the bloc's errant members, comments that were echoed by Mersch.

We need an institution that is solely in charge of the euro zone. This could be a commissioner with special powers or a finance minister...or a different body, the ECB Governing Council member told Revue magazine in an interview.

We need stronger coordination at a European level. This also means the transfer of certain national powers to the European parliament.

Mersch, who also heads Luxembourg's central bank, also stuck to the ECB's line that it should not be dragged further into the arena of fiscal policy by effectively being forced to finance any bond buying by the euro zone bailout fund.

Here, we are saying no! We are dealing with fiscal problems. These should not be solved on the back of the currency. Otherwise the currency loses credibility.

Mersch said the ECB would stick to its single mandate of ensuring price stability. This is the soul of the ECB and I can't imagine that the soul is at stake, he said.

The euro zone crisis, which started in Greece, has spread to Portugal, Ireland and is now threatening to spillover to Italy and Spain.

European leaders are locked in talks on ways to expand the bailout fund's firepower, make Greece's debt burden more manageable and also prop up banks that have been hurt by the crisis.

The risk, however, is that the extra support needed could spark rating agency downgrades that could undermine the plans. Mersch warned if France was downgraded it would put other countries ratings in question.

If France was to be downgraded, we will see the situation of other countries through a different lens... It would then raise the question whether Europe like the United States still fulfils the AAA requirements, he said.