One Greek minister says a referendum this weekend on a bailout for the country will "mark" the future of the whole continent.

It comes as the International Monetary Fund (IMF) says Greece needs €50bn over the next three years to stabilize its finances even under existing creditor plans.

In a new report, the IMF acknowledged a huge deterioration in the country's prospects in recent months.

Details from the report emerged as police clashed with far-left protesters in Athens on Thursday night.

Officers used tear gas and pepper spray to stop demonstrators trying to storm EU offices in the capital.

The IMF report has slashed Greece's 2015 economic growth forecast to 0%, from 2.5% forecast in April.

Of the €50bn needed, €36bn must come from European Union lenders, the report added.

That estimate, too, was made before Greece broke off talks with official creditors last weekend and ordered capital controls.

Its banks have shut for a week, all of which has further stifled economic activity.

The new "preliminary draft" analysis of Greece's finances highlighted the deterioration since Prime Minister Alexis Tsipras took power at the beginning of 2015.

"Very significant changes in policies and in the outlook since early this year have resulted in a substantial increase in financing needs," the IMF said.

George Katrougalos is Greece's minister for administrative reform.

He told Newstalk Breakfast it is going to be a close vote, but they will respect the outcome.

Meanwhile the Tánaiste Joan Burton appears to have ruled out any further write-down of Greek debts

Bhe says Greece is likely to have its debts restructured, so that repayments will not be due until years into the future.

Ms Burton says Greece will have to step up to make sure the debts are delayed instead of written-off.

The European Commission wants Greece to raise taxes and heavily cut welfare spending to meet its debt obligations.

But Mr Tsipras has urged Greeks to vote "No" to the creditors' bailout proposals, saying a rejection will lead to a "better agreement".

Last night he said a deal with the country's creditors would be struck 48 hours after any rejection of the terms in the referendum.

European officials and the Greek opposition have warned a 'no' outcome Sunday could be tantamount to a decision to leave the Euro.

A strong 'no' vote, Mr Tsipras argued, would help Greece win a new deal with the Eurozone's rescue mechanism.

This would include terms to make the country's €320bn national debt sustainable.