Frauke Petry, the co-leader of the far-right Alternative for Germany (AfD), said on Tuesday she would leave the party that became the third largest group in parliament after Sunday's national election, German media reported.
"It's clear that this step will follow," Petry was cited as saying by several German media including Spiegel Online and newspaper websites. She did not say when she would quit, they added.
The AfD was not immediately available to comment.
Petry, the highest-profile figure in the AfD's more moderate wing, had on Monday shocked other senior party figures by saying she would not sit with the AfD in the Bundestag lower house and would instead be an independent member of parliament.