PASOK, which shrank from 33 to 27 deputies after Parliament's vote on the new austerity package late Wednesday, looks set to lose one more MP as Mimis Androulakis on Thursday announced he's quitting the once-dominant Socialist party.

In an interview with To Vima radio on Thursday, Androulakis, a writer and former member of the Greek communist party, also said that he would vote against the new budget on Sunday.

On Wednesday, Androulakis voted in favor of a controversial package of cost-cutting measures demanded by the country's foreign lenders. He had earlier said he would oppose the measures.

The package was approved with a tissue-thin majority as tens of thousands of demonstrators ringed the House.

Meanwhile, another PASOK heavyweight, Andreas Loverdos, on Thursday called for an urgent meeting of the coalition partner's parliamentary group. Loverdos is widely seen as one of the challengers to embattled party chief Evangelos Venizelos.

In a letter sent to Venizelos on Thursday, the former health minister said a meeting was necessary to discuss the “deep crisis” plaguing the party.

Recent surveys have polled PASOK at fifth place.