The junior partner in the Irish Republic's governing coalition has called for a general election in January, after an EU-led bail-out of the country's ailing economy.
The Green Party said the Irish people needed "political certainty".
The government has accepted up to 90bn euros (£77bn; $124bn) of EU-led loans and will publish a four-year budget plan on Wednesday.
The opposition Labour Party also called for the dissolution of parliament.
Labour leader Eamon Gilmore said it was "essential that we have a new government elected as soon as possible".
He said: "My preference would be for a dissolution of the Dail (parliament) today and the holding of a general election at the earliest possible date.
"This would allow the election of a new government by the middle of December."
The Greens, with six lawmakers, hold the balance of power in the governing coalition.
Even with Green Party support, the government of Prime Minister Brian Cowen has just a three-seat majority in parliament and faces a by-election in one of those seats on Thursday.
In a statement, Green Party leader John Gormley did not say the party was pulling out of the coalition but he made a number of demands and said a general election date should be set for the second half of January.
The BBC's Mark Simpson in Dublin says the economic turmoil has now sparked a political crisis.
He says the Green Party is likely to get its way on a general election, though in theory this will not stop the EU-led bail-out or the budget, which will be unveiled on 7 December.
The ruling coalition also relies on two independent MPs. Both said on Monday they could not give a commitment that they would support the budget.
The main opposition party, Fine Gael, has said it will discuss on Tuesday whether or not to support the budget.
Mr Gormley, also the environment minister, stressed the election should only be held after the 2011 budget had been passed.
"Leaving the country without a government while these matters are unresolved would be very damaging and would breach our duty of care," he said.
Mr Gormley added: "The past week has been a traumatic one for the Irish electorate. People feel misled and betrayed.
"But we have now reached a point where the Irish people need political certainty to take them beyond the coming two months."
Ahead of any election, Mr Gormley said the government had to:
- Produce a credible four-year plan to show the country could make its budget balance by 2014
- Deliver a budget for 2011
- Secure funding support from the EU and IMF which would respect vital Irish interests and restore stability to the Euro area
Mr Gormley said there had been "bad communication" within the government.
He also said Mr Cowen had expressed disappointment at the Greens' decision.
Mr Gormley did not spell out the Greens' future role in the coalition, only saying: "Despite our difficulties and disappointments, I believe we can get out of this situation. We must all work together to ensure the best outcome for everyone."
Former Irish PM John Bruton told the BBC the Greens had done the right thing to "bring certainty to the situation".
"The reality of it is that we will be having a general election campaign where the choices will be laid out for the people," he said.
European shares and the euro both fell following the election call from the Green Party.
They had risen in earlier trading, after the announcement of the bail-out.
The UK is expected to contribute about £7bn of the bailout. Chancellor George Osborne said: "Ireland is a friend in need, and we are here to help."
The BBC's Mark Simpson says this is a demonstration of the close economic links between London and Dublin. Political relations are good too, he says, but it is likely that within two months the UK will be dealing with a different Irish government.
The crisis in the Irish Republic has been brought on by the recession and the almost total collapse of the country's banks.
Once known as the Celtic Tiger for its strong economic growth - helped by low corporate tax rates - the country has experienced a property bubble burst, leaving its banks with huge liabilities and pushing up the cost of borrowing for them and the government.