DUBLIN (Reuters) - Finland's Europe minister Alexander Stubb questioned the need for a change to the European Union's treaty, saying such a move would require too much time and raise uncertainty.

European Commission President Jose Manuel Barroso last week called for the European Union to be turned into a 'federation of nation states', a vision he said would require an overhaul of the Lisbon Treaty.

"If treaty change is needed, then it must be done. However, I am slightly skeptical as to the real need for treaty change and also cautious about its feasibility," Stubb, Minister of European Affairs and Foreign Trade, said in prepared remarks during a visit to Dublin.

"I would disagree with President Barroso when he said that we cannot move forward under the existing treaties."

A significant treaty change would trigger referendums, which would increase uncertainty, he said.

"I would take great precaution in introducing elements like treaty change or federalism into the equation, perhaps raising the bar of fixing the euro from the concrete and achievable to the theoretical and unachievable," he said.

Some members of the European Parliament, including committed pro-Europeans such as former Belgian prime minister Guy Verhofstadt, have also spoken out against Barroso's call, saying the EU needed to deepen the structure already in place, not become a federation of nation states.

Barroso, a former Portuguese prime minister, has said his office would flesh out proposals for the future shape of the EU, including the legal changes required to become a federation, before mid-2014.

Stubb also said the European Commission was right in seeking integrated supervision over the region's banks, but said such a move would be "toothless" without the power to close non-viable banks.

"Bank resolution needs to be a part of the plan," he said.

The Commission wants to give the European Central Bank responsibility for monitoring all the euro zone's banks, although Germany wants only the biggest, systemically important banks to come under ECB supervision.

(Reporting by Padraic Halpin; Writing by Ritsuko Ando; Editing by Susan Fenton)