The head of Greece's conservative party, Antonis Samaras, announced late on Tuesday that he would not back a further €6bn austerity measure to reduce the country's deficit.
The political stalemate over austerity measures is threatening to jeopardise the country's next tranche of a €110bn bailout worth €12bn, which is due in June.
Greece announced on Monday the immediate sale of state assets including the ports of Piraeus and Thessaloniki, and shares in OTE, Greece's telecom operator.
Prime Minister Georgios Papandreou pledged to go ahead with the drastic privatisation plan in an attempt to reduce its elevated debt level.
In a televised speech to his ministers, Papandreou said: “Through our decisions and the sacrifices of the Greek people we avoided bankruptcy last year. We now need to take the necessary decisions to avoid the danger once and for all, and to change the country.”