The cost of insuring Portuguese debt against default rose on Monday after a strong election result in Finland for a party opposed to a bailout of Portugal. Greek, Irish and Spanish credit default swaps also rose after a report, later denied, that Greece had been seeking a debt restructuring. Amid the public's clamouring for a debt default, the head of the Greek central bank said a restructuring is not needed and would be catastrophic for the country, hitting bank and pension fund assets and closing off access to capital markets.

The euro fell to a ten-day low against the dollar, hitting $1.4302, and its lowest in more than two weeks against the yen amid growing fears over the eurozone debt crisis.

A new round of bailout negotiations between the Portuguese government and the International Monetary Fund (IMF) and European Union began as a Finnish anti-euro party vowed to derail the rescue. Portuguese five-year credit default swaps climbed 26 basis points to 625bps this morning, according to data monitor Markit. Debt premiums also hit new record highs in early trading. The premium investors demand to hold Portuguese benchmark 10-year bonds rather than safer German Bunds rose to 599 basis points from Friday's 583 bps, and the 10-year yield hit 9.34%.

The True Finns more than quadrupled its share of the vote to 19% and finished a close third in parliamentary elections at the weekend. The party expects to hear later this week about joining talks on forming a coalition, which could turn Finland's traditionally pro-EU politics on its head. The party leader said he expects the EU to change plans for a bailout of Portugal. "Of course there will have to be changes," Timo Soini said. "The package that is there – I do not believe it will remain."

The cost of insuring Greek debt soared after a newspaper report that the country had asked the IMF and the EU to restructure its debt, although this was later denied by Greece's finance ministry. Furious Greeks are urging their government to default on its debt as the country struggles to dig itself out of its crisis despite a €110bn (£97bn) bailout. Five-year credit default swaps on Greek government debt surged by 84bps to 1220bps. This means it costs €1.22m to protect €10m of exposure to Greek bonds. Irish and Spanish credit default swaps also rose.

Bank of Greece governor George Provopoulos, also a member of the European Central Bank's governing council, said in a report to shareholders: "The Bank of Greece has explained with clarity since last October that such a [debt restructuring] option is not necessary, nor desirable. It would have catastrophic consequences."

It remains unclear to what extent a new Finnish coalition, which could take weeks to form, will incorporate True Finns' ministers or their views on EU support for heavily indebted member states. But the rise of the True Finns seems likely to shift the debate. "This is a big, big bang in Finnish politics. This is a big, big change. This will change the content of Finnish politics," Jan Sundberg, a professor at the University of Helsinki, told Reuters.

Unlike others in the eurozone, Finland's parliament has the right to vote on EU requests for bailout funds, meaning it could hold up costly plans to shore up Portugal and bring stability to debt markets. The strong showing for the populist True Finns reflects growing public frustration in some EU states about footing the bill for weaker economies such as Greece, Ireland and Portugal.

Dominique Strauss-Kahn, the head of the IMF, said at the weekend that Europe needed to come up with a more coherent plan to deal with government debt following the bailouts of Ireland and Greece. He criticised piecemeal attempts to resolve individual countries' debt problems. He also criticised Britain's refusal to support a funding package to tackle the eurozone crisis.