The three leaders are meeting in Berlin next month

Mr Frattini's criticism comes ahead of an 18 February meeting between French, German and British leaders in Berlin.

The three-party talks are meant to prepare for an EU summit in March.

French President Jacques Chirac spoke recently of a "real willingness" between the three to be "the driving force behind tomorrow's Europe".

Mr Frattini, who was reporting to the Italian parliament on the results of the recent Italian EU presidency, said he was against the idea of a "directoire" running the EU.

"There cannot be a directoire, there cannot be a divisive nucleus which would run the risk of posing a threat to European integration," he said.

President Chirac, Chancellor Gerhard Schroeder and Prime Minister Tony Blair met in September and again in December to patch up their differences over the war in Iraq and adopt a common approach before the EU summit on constitution.

An EU summit in Brussels in December ended in failure when negotiations broke down over how voting will work when the EU expands from 15 to 25 members in May.

Poland and Spain insisted on keeping voting rights already secured, while France and Germany wanted a system to reflect their bigger populations.

'Pioneers'

Mr Chirac told reporters after the summit that he wanted to see a "pioneer group" of countries which wanted to push ahead with integration.

"It would be a motor which would set an example," he said. "It will allow Europe to go faster, better."

German Chancellor Gerhard Schroeder also said a definitive failure to agree a constitution could lead to a "two-speed Europe".

UK Foreign Secretary Jack Straw signalled last week that the UK was keen to be a member of the core team.