Police have searched the home of the leader of the far-right Alternative for Germany (AfD) party in Potsdam, reported the Süddeutsche Zeitung newspaper.  

The development came after the German federal parliament, the Bundestag, agreed to lift the immunity of AfD co-leader Alexander Gauland, to allow for "search-and-seizure decisions ordered by a court" to be carried out. 

Der Spiegel, a German weekly news publication, was cited by AP as reporting that prosecutors in Frankfurt are investigating whether Gauland, 78, failed to submit his personal taxes correctly. 

An AfD spokesperson said: "We consider the investigation process and measures to be unjustified and disproportionate." 

Lawmakers also lifted the immunity of Karin Strenz, a member of Chancellor Angela Merkel's Christian Democrats (CDU). The precise reason for the investigation against Strenz was unclear.  

Bundestag members have immunity by default. Police can only investigate and arrest members if the body agrees to waive immunity. The regulation is intended to protect members against pressure from the judiciary. 

The inquiry into Gauland is separate from an investigation into his fellow AfD leader in parliament, Alice Weidel, who is under scrutiny over possible illegal party funding. She denies the allegation. 

Gauland was criticized earlier this week for appearing to sleep during a speech given by Israel's president, Reuven Rivlin, to the German parliament marking 75 years since the liberation of Auschwitz. 

In 2018, Gauland told an AfD junior staff organization that "Hitler and the Nazis are just a bird s**t in over 1,000 years of successful German history."