New European Commission chief Jean-Claude Juncker accused British Prime Minister David Cameron Wednesday of having a "problem" with other EU leaders, stoking a bitter budget battle between London and Brussels.
Juncker opened his first press conference as head of the EU's powerful executive arm with an attack on what he called unjustified criticisms by both Cameron and Italian Prime Minister Matteo Renzi at a summit in October.
But he reserved his harshest words for Cameron, who is fighting Brussels over a budget backpayment demand for 2.1 billion euros ($2.6 billion), against the backdrop of a possible referendum on Britain's EU membership in 2017.
"I am not the type who trembles, in front of prime ministers or at any other time," said former Luxembourg prime minister Juncker after chairing the first meeting of his new Commission after taking over from Jose Manuel Barroso on Saturday.
"I don't have a particular problem with Mr Renzi, whom I have great respect for.
"I don't have a problem with Mr Cameron, Mr Cameron has a problem with the other prime ministers."
Juncker's comments came a day after he criticised Cameron and Renzi, telling the European Parliament that the British and Italian premiers had misled their citizens by saying one thing during the summit and another to the media afterwards.
Cameron had said he confronted other leaders at the summit, bluntly refusing to pay the bill imposed by the Commission as a result of revised figures from EU member states, and saying it had been "unacceptably" sprung on Britain.
Renzi meanwhile had vowed at the summit to make public the cost of European Union "palaces" in a row over Italy's own budget projections.
- 'Gang of bureaucrats' -
On Tuesday, Renzi hit back in a television interview and demanded "respect" from Juncker.
"I'm not going to go to Brussels to have what needs to be done explained to me, and I told Barroso and Junker that," he said.
"I'm not going to Europe to say 'please listen to us', I'm not going with my hat in hand."
Juncker angrily responded on Wednesday, saying that he would defend the Commission -- which drafts laws and enforces financial rules for the 28-member bloc -- against "unjustified criticisms".
"I am not the chief of a gang of bureaucrats. We are senior officials, we are political men," he told the press conference.
"To say that the Commission must not interfere in dossiers that fall under the EU economic coordination, to say that one will not take lessons from Brussels bureaucrats, these things I dislike."
Cameron strongly opposed Juncker's appointment as Commission president earlier this year, describing him as an insider and federalist who would not bring in the EU reforms that Britain demands.
The British Conservative premier has vowed to renegotiate Britain's relationship with the EU then hold a referendum in late 2017, provided that he is re-elected next May.
He has had a series of stand-offs at summits with other European leaders in recent years, holding up a crucial fiscal pact aimed at tackling the euro crisis as well as the EU's 2014-20 multi-year budget.
Meanwhile Juncker is a seasoned politician and European insider, who led Luxembourg for 19 years and also headed the Eurogroup of finance ministers that use the euro at the height of the single currency's debt crisis.
He won a reputation for plain speaking and also for standing up against the more powerful EU states, particularly Germany when the economic powerhouse sought to wield its influence.