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.