The Social Democrats have called for the right-wing People's Party to be expelled from government. The statement comes amid political jockeying over who will succeed the outgoing People's Party cabinet minister, Adolf Ogi.
The Social Democrats said on Wednesday they did not want a People's Party member to take over Ogi's position when parliament meets to elect a successor on December 6.
They said the People's Party was no longer prepared to be part of a unified federal government.
The government is made up of four parties under a "magic formula" which has existed for 41 years. The People's Party has one of the seven cabinet seats.
The Social Democrats said the People's Party was dominated by its right-wing faction, led by billionaire businessman Christoph Blocher, and that his policies and tactics were directed against the state and its institutions.
"By systematically discrediting our political class, the People's Party is destroying the culture of dialogue in our country," the Social Democrats said.
The Social Democrats' move, and suggestion that the People's Party seat should go to one of the two centre-right government parties, the Radicals or the Christian-Democrats, was immediately rejected.
Hilmar Gernet, secretary-general of the Christian-Democrats, said the Social Democrats' proposition was part of the show surrounding the Ogi succession.
"The Social Democrats attitude is naïve," said Guido Schommer, the Radicals secretary-general. "The first consequence of this is that they are putting themselves out of any serious talks about the Ogi succession."
Blocher's Zurich section of the People's Party on Wednesday nominated Rita Fuhrer, president of the cantonal government as its candidate to succeed Ogi.
Other candidates who have come forward so far include two senators, Christoffel Brändli of canton Graubünden and Samuel Schmid of canton Berne, and the president of canton Thurgau's government, Roland Eberle.
swissinfo with agencies