Photo:VCG

 
Swiss voters' concerns about climate change look set to give the environmentalist Greens strong gains in a parliamentary election on Sunday that could dilute the centre-right's grip on power.

A solid showing by the Greens could vault them and allies into the mix for a seat in the grand coalition that has governed the conservative nation for decades. Changing just one member of the seven-seat cabinet would be a political sensation.

A Sotomo poll this month for broadcaster SRF showed the right-wing Swiss People's Party (SVP), which won record seats in 2015 amid Europe's refugee crisis, will dip 2.1 points to 27.3 percent while the Green Party's share will rise more than 3 points to 10.7 percent of the vote.

The smaller, more centrist Green Liberal Party (GLP) is also expected to advance, bringing their combined strength to a theoretical 18 percent.

That would place them collectively third behind the SVP and the centre-left Socialists (SP), ahead of the centre-right Liberals (FDP), who all have two of the seats on the Federal Council that is Switzerland's government.

Cabinet seats have been divvied up among the SVP, SP, FDP and Christian People's Party (CVP) in nearly the same way since 1959.

In December, the two parliamentary chambers will elect the government.