German Chancellor Friedrich Merz faced a rising chorus of criticism from within his own centre-right CDU party Wednesday as he completed a chaotic cabinet reshuffle.

Complaints over Merz's high-handed leadership style have boiled over after the personnel changes prompted by the resignation of the CDU's parliamentary leader Jens Spahn.

Spahn had to step down this month after it emerged he and his husband had had a child via a surrogate mother in the United States, despite the practice being illegal in Germany and vehemently opposed by the CDU.

CDU lawmakers will meet on Wednesday to formally elect Spahn's successor Thorsten Frei, Merz's chief of staff.

At that meeting Merz may have to face the music from lawmakers angered by the way he conducted the reshuffle, including the botched sacking of transport minister Patrick Schnieder.