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.

German election frontrunner Friedrich Merz succeeded on Wednesday in getting a motion passed in parliament that calls for a migration crackdown including the rejection of asylum seekers at the country's land borders.

Germany’s parliament has narrowly approved a call by Chancellor Olaf Scholz’s main challenger to turn back many more migrants at the country’s borders, with the help of a far-right party.

The CDU party chief, who leads in the polls to become the next chancellor, said he would collect votes from all parties to push his five-point migration plan through parliament despite Chancellor Olaf Scholz's strong opposition.

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.