Former German Chancellor Angela Merkel on Thursday 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 center-left governing parties have cast doubt on whether conservative leader Friedrich Merz can still be trusted not to bring the far-right Alternative for Germany, or AfD, into government after Wednesday's events.