The rightwing Swiss People's Party is facing increasing internal tension in a row over Justice Minister Eveline Widmer-Schlumpf.
Liberal members of the Bern cantonal chapter have announced they are planning to set up their own party to protest against the hardline policy of the national leadership.
The opponents include Defence Minister Samuel Schmid – who has been sitting in the cabinet for more than seven years.
Party officials said Schmid's announcement that he was willing to join the new group showed that he was a true representative of the party line.
On Sunday the national leadership moved to ban the Graubünden chapter amid accusations it supported Widmer-Schlumpf.
She accepted her election to cabinet against the wishes of the national party in December after the party strongman Christoph Blocher was voted out.
The People's Party won 29 per cent of the vote in last year's parliamentary election and is the biggest of the four main political parties.
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