Greece's 2009 budget deficit was worse than previously calculated, making it the largest in the eurozone, new figures have shown.
The country's deficit last year stood at 15.4% of its annual economic output, said Eurostat, the European Union's statistics office.
This is higher than the 13.6% figure reported in April.
Due to the revision, Greece said its 2010 deficit would only be cut to 9.4%, not its earlier target of 7.8%.
It comes as Athens is continuing efforts to reduce the deficit through austerity measures that have sparked protests from workers.
The Greek government is also being visited by EU and International Monetary Fund officials on Monday, who will decide whether to release more funds.
Greece is seeking the third part of its 110bn euros ($150bn; £93bn) aid deal, which was arranged in May.
Prime Minister George Papandreou said over the weekend that Greece might be forced to ask for an extension to the time before it has to start repaying aid money.
The Greek government said Eurostat had revised up the 2009 deficit figure for three main reasons; a downward revision of the country's economic growth rate that year, an adjustment of social security funds, and by adding data from certain public sector bodies into the general government figures.
As a result, its 2009 deficit of 15.4% overtook the Republic of Ireland's 14.4% figure, which was previously calculated as the worst.
Eurostat also revised upwards the total level of Greece's debts in 2009 to 126.8% of its GDP from 115.1% previously. It predicts the country's debs will hit 1445 this year.
The European statistics office had been concerned that its earlier 2009 deficit figure for Greece had been incorrect. Its new final is its final calculation, and it said it no longer had any reservations.
Greece's Ministry of Finance said: "The revision and validation of the fiscal data up to 2009 is a major step to restore transparency in fiscal management, and to eliminate controversies over the quality and the accuracy of Greek fiscal statistics."
Eurostat said last week that Greek economy had contracted by -1.1% between July and September, better than the -1.7% decline from April to June