The Czech Republic's president Milos Zeman is under fire for refusing to confer a professorship on a renowned historian, reportedly because of the academic's support for gay rights.

In an unprecedented move, Zeman refused to approve university officials' appointment of leading Czech Catholic literature expert Martin Putna as professor.

Zeman denied his decision had anything to do with Putna's open support for his opponent at January's presidential elections or the academician's sexual orientation.

Zeman refused to fully explain his stance, saying he did not want to "humiliate" Putna "by naming the reasons publicly".

He did not hide his angerm however, at Putna unfurling a banner mocking Ladislav Bátora, an ultra-conservative politician and former public official, at a 2011 gay pride parade.

"It's something entirely different when you walk around Prague with a sign that says, 'Catholic queers salute Bátora'," Zeman told Radio Praha.

His refusal to rubberstamp the appointment has caused an outcry in the Czech academic and political world. It condemned his action as an unacceptable intrusion into academic matters.

Under Czech law professorships conferred by universities have to be formally approved by the president. Zeman's predecessors normally waved decisions through.

The rector of Charles University, where Putna works, has reportedly demanded an official explanation.

Martin Putna
Martin Putna at the 2011 gay pride parade in Prague (Courtesy of Radio Praha)