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.

Germany's opposition conservatives won parliamentary approval on Wednesday for a proposal to drastically restrict migration with the help of votes from the Alternative for Germany (AfD), breaking a taboo on cooperation with the far-right.

With less than four weeks before Germany’s federal election, Chancellor Olaf Scholz and his conservative challenger Friedrich Merz, who is leading polls, will take their contentious battle over how to crack down on illegal migration to parliament.