AfD became the third largest group in parliament after Sunday’s national election, German media reported.
“It’s clear that this step will follow,” Fraulein 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.
Fraulein Petry is currently state spokesman and chairman of the Saxony AfD state association.
In 2014, she moved into the Landtag of Dresden, where she led the party in parliament. She will also resign this office. Uwe Wurlitzer, the parliamentary director and Kirsten Muster the vice-chancellor of the parliamentary group, were also going to give up their office in the group “at some point today”, Fraulein Petry said.
The AfD was not immediately available to comment.
Fraulein Petry, the highest-profile figure in the AfD’s more moderate wing, had yesterday 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.
She said that the party became too “anarchical” and “could not offer a credible platform”.
According to media reports, the North Rhine-Westphalian AfD chief Marcus Pretzell is also leaving the party in the Düsseldorf parliament.
The AfD had gained 7.4 percent of the votes in the most populous federal state during May, and has 16 seats in Parliament since.
Herr Pretzell and Fraulein Petry have been married since December 2016 and have a child together.
In Schwerin at the beginning of the week, four former AfD Landtag deputies had formed their own group in the Schwerin Landtag.
In the meantime, the remaining 93 Bundestag deputies of the AfD met in Berlin to decide their aims.