At issue is whether the fiscal rule, which would require budgets to be balanced or in surplus in good years while setting a debt ceiling in a downturn, can be implemented in 2015 as originally planned.

The government has said that the enacting it in 2015 would require unacceptable spending cuts to the tune of EUR 800m next year and has therefore sought to postpone its implementation to 2017.

"Amending the Constitution with something that we will not honour is totally unrealistic," Prime Minister Alenka Bratušek said after the meeting.

"As prime minister, I will not advocate taking 30% away from pensioners, doctors and teachers while leaving those who are already on the margins without anything," she said.

However, the opposition, in particular the Democrats (SDS), insists that the fiscal rule needs to take effect in 2015 in order to send a strong signal to financial markets.

The SDS's refusal to budge was underlined today by the absence of the party's president, Janez Janša, at the meeting, which had already been postponed once because Janša said he was unable to attend due to preparations for the 11 May party congress.

It was decided today that the National Assembly session scheduled for Monday at which tighter referendum rules were to be adopted would be postponed.

The Tuesday session, dedicated to the fiscal rule, remains on the agenda, but Bratušek said all parties bar the SDS had agreed to postpone it as well so it remains unclear whether it will be held.

The government wants to reschedule it in order to present the Stability Programme, a set of measures that the government must sent to Brussels next week.

Based on these specific measures, it would then be decided when is the best time to implement the fiscal rule, according to Bratušek.

She has given the SDS until Tuesday to decide whether to accept a compromise. It therefore remains unclear whether, if there is a session in the first place, the MPs will vote to send the legislation implementing the fiscal rule back to the Constitutional Commission for amending, as the government wants, or not.

Bratušek also pointed to a possible way out, noting that Germany adopted a fiscal rule in 2009 but deferred its implementation until 2016 at the national level and until 2020 at state level.

Implementing the fiscal rule in a year and a half is "unrealistic" unless "someone has the interest to turn this country into something else than a welfare state," she said.

Changes to the Constitution require a two-thirds majority in parliament and given the refusal of the coalition Social Democrats (SD) to endorse it, Bratušek needs SDS votes.

SD leader Igor Lukšič said today his party would not vote in favour of the constitutional amendment, it is, however, willing to support a special law on the fiscal rule which would be confirmed with a two-thirds majority.