The nomination of Joachim Gauck, a firebrand former Protestant pastor and civil rights activist, as Germany’s federal president has left chancellor Angela Merkel facing a rare political humiliation.

Tensions in Ms Merkel’s ruling centre-right coalition exploded into the open yesterday, after the chancellor was forced to accept Mr Gauck’s nomination by an alliance of the liberal Free Democratic party, her junior partners, and the opposition Social Democrats and Greens.

Ms Merkel was forced into three days of frantic negotiations over the presidency – a largely ceremonial but nonetheless influential job – after the resignation on Friday morning of Christian Wulff, who is under investigation by prosecutors over allegations that he received improper favours.