Papandreou Greek referendum plan sparks early poll call
The main Greek opposition party has called for early elections after Prime Minister George Papandreou said he would hold a referendum on the proposed EU bailout plan.
Conservative leader Antonis Samaras said the referendum plan put Greece's EU membership at risk.
Separately, one of Mr Papandreou's MPs has defected, leaving him with a majority of two seats, 152 out of 300.
The Greek parliament will vote on a motion of confidence on Friday.
European markets fell sharply on Tuesday over fears the EU bailout was already unravelling.
Last week, eurozone leaders agreed on a 100bn-euro loan (£86bn; $140bn) to Athens and a 50% debt write-off.
In return, Greece must make deep cuts in public spending, slashing pensions and wages, and making thousands of civil servants redundant.
Another MP from Mr Papandreou's centre-left Pasok party, Vasso Papandreou (no relation) called for a government of national unity.
"I call on the president to convene the council of political leaders with the goal of forming a government of national salvation in view of safeguarding the EU package agreed on 27 October, and then to immediately hold elections," said Ms Papandreou, who chairs the parliamentary committee on economic affairs.
Mr Samaras, leader of the main opposition New Democrats, met Greek President Karolos Papoulias for talks on Tuesday morning.
"In order to save himself, Mr Papandreou has posed a dilemma of blackmail that puts our future and our position in Europe in danger," Mr Samaras said after the meeting.
"Elections are a national necessity," he said, adding that his party would avert "opportunistic experiments" such as the proposed referendum.
The next elections are not scheduled until 2013.
Opinion polls in Greece show that most people do not support the austerity deal. The most recent general strike, on 19-20 October, brought tens of thousands out onto the streets nationwide.
No date for the referendum has yet been announced, but Mr Papandreou indicated it would take place in a few weeks' time, once the details of the bailout package have been finalised.
He also ruled out early elections, saying they would be negative for the country.
Mr Papandreou has called a vote of confidence in his government for Friday.
Meanwhile, Greek Finance Minister Evangelos Venizelos was taken to hospital on Tuesday morning, suffering from stomach pains.
His office said he was likely to be released by the evening.
Mr Venizelos was given no warning that Mr Papandreou intended to call a referendum, an anonymous source told the Reuters news agency.
"Venizelos had no idea about the referendum. All he knew about was the vote of confidence," a government official told Reuters on condition of anonymity.
"He told Papandreou he should inform foreign partners and a letter was drafted in the early morning hours."