Six leading members of Greece's governing Pasok party have called on Prime Minister George Papandreou to resign, the day after he called a referendum on the proposed EU bailout.One MP has defected from Pasok, cutting Mr Papandreou's parliamentary majority to two seats - 152 out of 300 - ahead of a confidence vote on Friday.
The opposition has called for early elections, saying the referendum jeopardises Greece's EU membership.
European markets have fallen sharply.
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.
'Blackmail' Earlier on Tuesday, Pasok MP Milena Apostolaki quit the parliamentary group but said she would keep her seat to fight the referendum as an independent.
"I have an obligation to resist this erroneous political choice that divides the nation," she said.
Shortly afterwards, another MP from Mr Papandreou's centre-left Pasok party, Vasso Papandreou (no relation) called for a government of national unity, to be followed by snap elections.
I say "while it lasts" because the opposition is mobilising a parliamentary manoeuvre to bring down the government, which may succeed - returning Europe to its status quo of containable trauma.
If Greeks reject the 50% controlled default on debts they owe to the banking sector, then the arithmetic I revealed on Newsnight on the eve of the Euro summit comes into play - without a 50% haircut, and a further 130bn euro bailout, on top of 110bn, Greek debt spirals out of control and the country goes bust.
"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.Antonis 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.
European markets have fallen sharply since the announcement of a Greek referendum.
German Chancellor Angela Merkel and French President Nicolas Sarkozy announced they would hold talks on Greece with the EU, the International Monetary Fund (IMF) and eurozone leaders at the G20 summit in Cannes on Wednesday.
In a joint statement, Mr Sarkozy and Mrs Merkel said they were "determined" to implement the Greek bailout plan "as quickly as possible".
The head of the Athens Chamber of Commerce, Constantine Michalos, told the BBC he thought the decision to hold a referendum was a "suicidal" move.
"I've always indicated that the last thing the Greek economy needs is an early election - however after this totally irresponsible political move I don't think there is any other solution at the moment.
"We saw the financial markets literally crumble, the Greek stock market has had an absolute battering and of course the euro has dropped. So a lengthy period of non-government will be disastrous not just for the Greek economy but overall for the European economy."
The next Greek 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 on to 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 government official told the Reuters news agency, on condition of anonymity.
"Venizelos had no idea about the referendum. All he knew about was the vote of confidence," he said.
"He told Papandreou he should inform foreign partners and a letter was drafted in the early hours.
"Elections are a national necessity," he said, adding that his party would avert "opportunistic experiments" such as the proposed referendum.
taken from http://www.bbc.co.uk/news/world-europe-15538809