German conservative leader Friedrich Merz is set to take his hard-line immigration push to the next level despite a growing backlash over his move this week to force a resolution through parliament with backing from the far right.

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.

A who's who of German talent signed an open letter calling for political leaders to "uphold democratic values" after a historic vote in the Bundestag that saw anti-immigration proposal pass with the support 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.

A 99-year-old Holocaust survivor said on Thursday he would return his federal order of merit award to the German state in protest over a parliamentary vote in which support from the far-right was used for the first time to secure a majority.

Protesters in Germany on Thursday rallied against the conservative CDU party to decry its cooperation with the far-right AfD in pushing through parliament a motion to demand a crackdown on immigration.