Finland's finance minister threatened to pull her country out of the euro zone's future bailout fund if decisions on how it operates are made by majority vote rather than the EU's current rule of unanimity, according to public broadcaster YLE.
"We will stick to this demand for unanimity," Finance Minister Jutta Urpilainen was quoted as saying on YLE's website on Friday.
Finland is against a proposal, originally raised by France and Germany, to change the EU's rule of unanimous decision-making for the European Stability Mechanism (ESM). It fears such a change would harm smaller countries' interests.
A group of legislators, after consulting constitutional guidelines, said on Thursday that Finland could not accept a change to the EU's rule of unanimous decision-making without two-thirds of its own parliamentarians agreeing to the move.
That condition is unlikely to be met with the No. 2 Social Democratic Party and both opposition parties against it, although the leading National Coalition is known for its pro-Europe stance.
Finland supports most other proposed measure to rescue the euro including automatic sanctions on euro zone deficit offenders, and analysts see a chance of some kind of technical compromise.
Yet in recent months it has made demands, such as a call for collateral on loans to Greece, that some critics say pander to growing anti-euro sentiment at home.
The Finns Party, previously known as the True Finns, gained seats in April elections after a campaign focused on criticizing EU bailouts and is now the third-biggest group in parliament.
"Euroscepticism is now louder," said Ville Pernaa, a researcher at Turku University's Centre for Parliamentary Studies.
Finland's demand is one of the disagreements dividing Europe over how to rescue the euro. At a summit meeting on Friday, a large majority of countries led by Germany and France agreed to tighter fiscal integration, but Britain said it could not accept proposed amendments to the EU treaty.