Former German Chancellor Angela Merkel criticized Friedrich Merz, her successor as leader of the country’s conservatives, on Thursday for pushing through a bill on tighter immigration control with the help of the far right.

Former German Chancellor Angela Merkel has issued rare public criticism of her successor as the country’s center-right leader, the front-runner in Germany’s election next month, for putting to parliament proposals for tough new migration rules that only passed with the help of a far-right party.

The vote, expected on Friday, adds to a controversy about the attitude of the front-runner in Germany’s upcoming election towards the far-right.