The new European Commission chief Jean-Claude Juncker has accused British Prime Minister David Cameron and his Italian counterpart of misleading their citizens over budget talks with Brussels.

He claims what Mr Cameron said publicly about the EU demand for stg£1.7bn (€2.16bn) contradicted what was said to other leaders behind closed doors at last month's summit.

Mr Cameron has refused to pay the bill, making clear he believed the call for extra cash and ensuing row undermined support for British membership of the EU.

The increase would add almost a fifth to the UK's annual contribution of stg£8.6bn (€10.9bn).

Brussels responded by warning the UK would face "late payment fines" if it failed to hand over the cash - which reflects changes in the relative national income of different EU states - by the 1 December deadline.

Referring to the October meeting, Mr Juncker told a European Parliament hearing: "I don't like the way that certain prime ministers behaved after the summit."

"I took notes and when I compared what they had said inside the room with what they said outside, they did not tally up."

His comments are set to further sour relations with Mr Cameron, who bitterly opposed Mr Juncker's appointment as commission boss.

France is the biggest gainer from the recalculation of national contributions to EU budgets, and is due to receive €1bn, while EU partners including the Netherlands, Italy, and even bailed-out Greece and Ireland face surcharges.

"I want prime ministers to respect these institutions"

Mr Juncker also took a sideswipe at the Italian leader Matteo Renzi, who vowed at the summit to make public the cost of European Union "palaces" in a row over Italy's budget projections, earning a sharp rebuke from then-Commission president Jose-Manuel Barroso.

"I said to Matteo Renzi that I was not the leader of some gang of bureaucrats," Mr Juncker said.

"I am the president of the European Commission, a political institution, and I want prime ministers to respect these institutions."

He also suggested Rome was lucky to scrape through an initial review by Brussels of its 2015 budget despite running an excessive deficit.

He said: "If Barroso only listened to bureaucrats, Italy's budget would have been treated differently."

Mr Renzi took to Twitter to hit back at Mr Juncker, demanding respect from Brussels for his country.

He said: "I'm not going to go to Brussels to have what needs to be done explained to me, and I told Barroso and Juncker that."