The New York Times reported on Sunday that a decade-long effort to skirt permissible European debt limits included tactics designed to obscure billions in debt from budget overseers in Brussels.

But finance minister George Papaconstantinou insisted that "derivated contracts" used to borrow money, without increasing official debt levels in the eyes of Brussels, were "at the time legal. And Greece was not the only country ... to use them," he said.

"Since they were made illegal, Greece has not used them," he underlined.

A spokesman for the European Commission, which has agreed new rules designed to ensure Greece and other deficit bingers provide accurate and up-to-date financial data, said Brussels has requested explanations from Athens by the end of February.

The Times said that as late as early November last year, a team from Goldman Sachs arrived in Athens with a plan that would have pushed debt from Greece's stretched healthcare system far into the future.

The newspaper compared the move to desperate homeowners who take out second mortgages to pay off credit cards, and notably detailed a 2001 transaction allowing billions borrowed to remain hidden from view, treated as a currency trade rather than a loan.

Greece has already been pursued by the commission for having used inaccurate data to meet conditions for entry into the eurozone at that time.