JYVASKYLA, Finland (Reuters) - Finland's eurosceptic Finns party picked an anti-immigration hardliner as its leader on Saturday in a move that the prime minister said might lead to a break-up of the ruling coalition.
At a Finns party congress, 56 percent of those voting backed European Parliament member Jussi Halla-aho, who wants Finland to leave the European Union.
Halla-aho, who was fined by Finland's Supreme Court in 2012 for comments on a blog that linked Islam to paedophilia and Somalis to theft, has said he will push the three-party coalition to tighten immigration policies, and that he will not stay in the government at any price.
"We must be more aggressive in raising the topics that distinguish us from other parties ... it is important to push our priorities forward more vigorously within the government programme," Halla-aho told reporters after his election.
Prime Minister Juha Sipila, citing differences in core values, said that there was a risk the centre-right government could break up due to Halla-aho's nomination.
"Of course (there is a risk of break-up). This is a tough spot for the government," Sipila, from the Centre Party, told daily newspaper Helsingin Sanomat.
The third coalition partner, the pro-EU National Coalition Party (NCP) also said it might not want to cooperate.
"This requires serious contemplation. The Finns party is not the same party anymore," Finance Minister Petteri Orpo told Verkkouutiset, an online news site.
As snap elections are very rare in the Nordic country, a break-up of the coalition would likely mean that Sipila would try to form a new one.
That could derail healthcare and local government reforms central to Sipila's plan to balance public finances.
Sipila is due to meet Halla-aho and Orpo on Monday.
The party congress also replaced all three deputy leaders with hardline anti-immigration politicians Laura Huhtasaari, Teuvo Hakkarainen and Juho Eerola.
Hakkarainen earlier this year was fined for a Facebook post calling for a Muslim-free Finland, which a district court said amounted to agitation against an ethnic group.
Formerly the True Finns, the party is known for having complicated EU bailout talks during the euro zone crisis.
But after becoming the second-biggest party in parliament in 2015, it joined the coalition government and accepted compromises, angering core voters.
Support for the Finns party has plunged from 17.7 percent in a 2015 election to about 9 percent in a poll this month.
Mari K Niemi, a researcher at University of Turku, said the party, which had sought to represent underprivileged people from rural areas, was becoming a more radical right-wing populist party.
"Young, sometimes educated people with an anti-immigration focus have become a more significant power within the party," she said, comparing the party's new profile to the far-right Sweden Democrats and France's National Front.
Finland is recovering from a decade of stagnation and problems including the decline of Nokia's former phone business. The government has sought to boost growth and curb public debt growth by cutting spending and reforming labour laws.
"If the coalition continues, it gets more and more difficult for the parties to agree on anything. And if the government broke up, a new coalition would surely change the current fiscal policy programme," said Nordea analyst Jan Von Gerich.
Outgoing Finns party leader and co-founder Timo Soini - a moderate populist who mostly focused on criticising the EU - stepped down after 20 years. It was unclear whether he would stay on as foreign minister.
Editing by Andrew Bolton