Timo Soini is excited about Italian bond yields. "I just heard that the interest on Italian 10-year loans is now over 7.3%," he whispers as a cast-iron lift hoists us from the ground floor of the monumental Finnish parliament to his office above. "This is a horrendous situation." But it's clear that, from his political standpoint, it's actually quite good news.

Soini, 49, is arguably the most successful eurosceptic politician in Europe today, and certainly in the eurozone.

Earlier this year, when his True Finns party refused to back the bailout of Portugal, this bear of a man (he's 18 stone and 6ft 2in) had the world's attention. "The Finns party made a huge impact last spring all over Europe," he remembers with satisfaction. "The Portuguese bailout was on the hook for nearly one-and-a-half months because of us."

The stance earned enormous political dividends. In the parliamentary election that April, the party won 19.1% of the vote, up from just 4.1% previously, turning a fringe far-right party into the country's third-largest, with MPs such as the glamorous Kike Elomaa, a former champion bodybuilder and pop star. The party received only slightly fewer votes than the once dominant Social Democrats.

The latest round of the eurozone crisis could not have come at a better time. Within a month, Soini launches his campaign for the Finnish presidency, and last week he returned from a tour of the UK and the US to begin agitating.

"We had a really, really fierce discussion, myself and the prime minister, yesterday in parliament," he tells me in his office. "I said, and it irritated the prime minister a lot: 'Have you ever heard about the Soviet Union? They said it was everlasting, and it was not. Now they say the euro and the European Union are everlasting, but it is not. If we run out of money and morals, there will be destruction one day.'"

Destruction seems to be part of Soini's plan. He says that Finland could easily retract the backing its parliament gave the expanded European financial stability facility, the eurozone bailout fund, in September, a move that would rip apart the rescue package stitched together last month. "We can even now say that it is full stop for our bailing out," he insists. "We can say it, even if we are members of the eurozone and the EFSF's [European Financial Stability Facility's] power has been enlarged. Each and every individual decision, by Finnish law, has to be made in this house, and if this house… says this is the end of the story, it's the stand of the Finnish parliament and we can do it."

With his lumbering build, baggy grey suits, football scarf and booming voice, Soini is a long way from the sober consensus politicians who built Finland's welfare state. He is well educated: his master's was, appropriately, on populism in politics. But he presents himself as an ordinary working-class guy and has a gift for witty, memorable soundbites which resonate well with the farmers and factory workers left out of Finland's technology-driven economy.

He's an anglophile who claims to have seen Millwall football club play 40 times. His greatest hero is John Paul II, who was pope when Soini converted to Catholicism, and whom he admires both for his opposition to communism and for his hard stance against abortion, contraception and women priests.

It's a sign of Soini's oratorical flair how easily he can turn all these peculiarities into assets. He claims that when he was 14 and saw Millwall play on television, he was drawn to their blue and white colours, which match the Finnish flag. "I didn't have the slightest idea of their reputation as so-called hooligans," he says. "But this has been used against me in this country. And of course, I can't just get rid of my team because somebody criticises it."

As for his religion, he uses it to identify himself both with Finland's minorities and with the southern European countries he so frequently condemns. "As a Catholic, I understand quite clearly the situation of Ireland, Poland, Italy and even Greek Orthodox countries. In Catholic countries the state isn't considered to be the hand of God. It's a common hobby to cheat the government, to cheat those who have power."

While Soini claims to be on the side of minorities, this isn't true for many of the other True Finn MPs. One, Teuvo Hakkarainen, last month suggested that all homosexuals and Somali refugees be exiled to an island in the Baltic. Another, Jussi Halla-aho, a blogger cited as an influence by the Oslo terrorist Anders Breivik, was found guilty of hate crimes after he wrote in 2009 that the Prophet Muhammad was a paedophile and Islam a religion of paedophilia. This September he argued that Greece would not be able resolve its problems unless it returned to a military dictatorship. Soini's only reaction so far has been to issue verbal warnings to Hakkarainen and suspend Halla-aho from the party for two weeks.

"You can't find a politician in this country who says that I have extreme views about foreigners or homosexuals or anyone else," he insists. "It's so painful to the old and established party to confess that there's a real challenger on economics, or bailing out the EU, that the easiest solution is to demonise us."

When Soini was in the US last week, he spoke on Fox News. Last month he spoke at the Conservative party conference in Manchester. "I get a massive amount of post throughout Europe. When they see that in Finland, which is a welfare country, which is a triple-A country, this kind of movement and party can rise here, it can rise everywhere. But that is what the people and the decision-makers haven't figured throughout Europe. They don't understand that people are not living only by bread, they are living on policy and they want to be heard."

He dismisses the arguments David Cameron used last week to defeat the Tory backbench calls for a referendum on the EU: "In a way he's right. Now might be a dangerous moment. But if things go in a better direction, then they'll say, 'There's no need because everything seems to function'."

He believes Germany may even turn against the EU: "Germany is paying in many ways for the sins of the Nazi government. German aircrews, they couldn't even go to Libya because of what Rommel did. But I think we will see also in Germany the rise of anti-bailout thinking, but it's so difficult to criticise it now without being labelled a certain kind of populist." Soini insists that his campaign is going to have a positive spirit.

"When do you need most hope? When there's no hope at all," Jukka Jusula, the spin-doctor who has run Soini's nine previous elections, explains softly.

Soini quickly picks up the theme. "Yes, when you are rowing in a galley. Do you remember? Where the slaves were rowing. Dum dum, dum dum," he continues, bashing away at imaginary kettle drums. "Then when the big stone is approaching… and crash," he says, smashing his fists together. "And you escape.

"Let my people go, says Moses to the pharaoh," he concludes with a prophetic roar. "Yes, let my people go! Why not?"