The basic premise of the rule is for the country to run without deficits in the medium and long term, in line with the EU's Fiscal Compact from 2012.

The first budget to fall under the rule will be for next year, but provisions in the act envisage gradual balancing of the structural budget with goal of achieving balance by 2020.

While implementing the debt brake after that period, the rule allows for exceptions in cases of extraordinary circumstances and recessions. The exceptions are focused mostly on protecting social transfers, pensions and the functioning of public institutions.

The implementation of the law will be overseen by the Fiscal Council as an independent body. Comprising three members, who will have to be macroeconomic experts, the council is to be appointed by the National Assembly with nominees put forward by the president, the central bank and the government.

The vote completes a process lasting three years of transposing the provisions of the Compact into its body of law.

In calling on MPs to back the implementation bill earlier in the day, Prime Minister Miro Cerar said it was high time that Slovenia enacts the rule and clearly shows its commitments to fiscal responsibility.

"Honouring the rule will stop the trend of the growing public debt due to excessive public spending," Cerar said, adding Slovenia was also the only EU member that had failed to deal with the details of the "golden rule" in its legislation.

In the uncertain circumstances that are a result of the situation with Greece, this undermines the position of our country on financial markets, Cerar argued ahead of the vote.

Finance Minister Dušan Mramor added that the bill did not automatically mean a lowering of social rights. Still, after years of crisis, Slovenia's GDP is substantially lower and public spending needs to adapt to this.

He warned that Slovenia was the last member not to have implemented the law among those which signed the Fiscal Compact and faced a lawsuit from the EU if it failed to pass it quickly.

Slovenia enshrined the fundamental principle in the Constitution in May 2013, but was running behind schedule in adopting legislation that defines its workings in practice, having promised to do so within six months after the constitutional amendment.

Requiring a two-thirds majority to pass, the bill received the votes of the coalition and, crucially, the opposition New Slovenia (NSi) and the Alliance of Alenka Bratušek (ZaAB), who came on board after six months of coordination with the government. The two minority MPs also voted in favour of the law.

Bratušek, the former PM under whose rule the fiscal rule was enshrined into the Constitution, said in its support that she would not like Slovenians to go down the path of the Greeks.

Parallels with Greece were also drawn by Matej Tonin of NSi and Jan Škoberne of the coalition SocDems. Škoberne pointed to the damage caused by excessive borrowing but also to that resulting from radical austerity. He feels the bill secures the right compromise.

The ruling Modern Centre Party (SMC) and Pensioners' Party (DeSUS) said they were fully on board the government proposal and the solutions used to ensure sustainability of finances on one hand and sufficient safeguards for action in time of downturn.

DeSUS lawmaker Franc Jurša said that the party was satisfied that the exceptions to the debt break meant that social rights, including pensions, were safe.

Voting against were the opposition United Left (ZL) and MP Janko Veber of the coalition Social Democrats (SD). The opposition Democrats (SDS) abstained.

The SDS had sought an amendment to the expenditure formula used to loosen the spending framework in the event of a small downturn but tighter caps on spending during boom years, but that was rejected today.

The ZL had been against the law throughout for fear that it will harm the welfare state. It has called for the rule to be removed from the Constitution.

Likewise, Veber argued the fiscal rule would hamper Slovenia's development. He said it would reduce wiggle room in setting fiscal policy in the country, which already had no independent monetary policy being a member of the single currency.