The president of the Green Party, Ruedi Baumann, has announced he is retiring after four years in the job.
The 54-year-old farmer said he had held the post for long enough and wanted to give his successor time to settle in before the parliamentary elections in two years' time.
A four-strong committee has already been appointed to find a successor who will be elected at the party conference on October 27 at Frauenfeld in canton Thurgau.
Baumann and his wife Stéphanie, who is also a parliamentarian, bought a 70-hectare organic farm in Gascony in southern France earlier this summer and have made it their official residence.
According to the Green Party, Baumann intends to remain a parliamentarian and to represent Swiss living abroad.
swissinfo with agencies