Former German leader Gerhard Schroeder, criticised for his relationship with Russian President Vladimir Putin, is suing Germany’s parliament.
Mr Schroeder, whose office and staff have been suspended, is suing over the removal of some post-retirement perks.
His lawyer told German news agency DPA on Friday that he had filed a suit with the Berlin administrative court.
The Bundestag said it was yet to receive the suit and could not comment further.
In its decision to strip him of the perks, the budget committee responsible concluded that Mr Schroeder, 78, “no longer upholds the continuing obligations of his office”.
But speaking to public broadcaster NDR on Friday, his lawyer Michael Nagel said the decision to suspend Mr Schroeder’s taxpayer-funded office was “contrary to the rule of law”.
He added that Mr Schroeder, who was in office from 1998 to 2005, had asked for a hearing before the committee, but was not given the chance to express himself.
A spokesperson for the Berlin administrative court confirmed that the lawyers had filed a complaint.
In May, Mr Schroeder stepped down from the board of Russian oil company Rosneft and also turned down a post on the supervisory board of gas giant Gazprom.
However, he has maintained close ties with the Kremlin.
He travelled to Moscow in late July for a meeting with President Putin, after which he said Russia was ready for a “negotiated solution” to the war in Ukraine.
These comments were branded as “disgusting” by Ukrainian President Volodymyr Zelensky.
Earlier this week, he survived a move to expel him from the local chapter of his Social Democrat party, with a committee saying there was no evidence that he had broken party rules.