French President Nicolas Sarkozy has said allowing Greece into the eurozone in 2001 was a "mistake".
He said Greece was "not ready" at the time. But, he added, it could be rescued thanks to Wednesday's EU deal on the euro debt crisis
In response, Greece's foreign minister told the BBC that Athens was not the source of the crisis, and that no country should be made a scapegoat.
The agreement reached in Brussels has triggered a worldwide shares rally.
In a TV interview on Thursday, Mr Sarkozy said admitting Greece to the eurozone had been "a mistake" because the country had "entered with false [economic] figures. It was not ready".
He added that he was confident the current Greek government would emerge from the crisis and that Wednesday's deal had averted a "catastrophe".
"If Greece had defaulted, there would have been a domino effect carrying everyone away," Mr Sarkozy said.
Speaking to the BBC, Greek Foreign Minister Stavros Lambrinidis said: "Greece is in the middle of the storm, but it is not the source of the problems of European debt and deficits.
"We see this with Portugal, Ireland, Spain and Italy. So it doesn't help to scapegoat a particular country when you're dealing with a European problem."
The comments come after European leaders clinched a deal at marathon talks in Brussels. The main provisions are:
- Banks holding Greek debt are to accept a 50% loss
- A new mechanism is to boost the eurozone's main bailout fund to about 1tn euros (£880bn; $1.4tn)
- Banks must also raise more capital to guard against losses resulting from any future government defaults
The agreement is aimed at preventing the crisis from spreading to larger eurozone economies, but the leaders said work still needed to be done.