The head of the Swedish Academy has resigned in a growing scandal over its handling of a sex abuse case that has also led three members to quit the panel that picks the winner of the Nobel Prize for Literature. 

Sara Danius stepped down on Thursday after criticism of how the institution handled a probe into allegations of sexual misconduct by a man married to one of its members. 

"It was the wish of the Academy that I should leave my role as Permanent Secretary," Danius, who has held the post since 2015, told reporters.

The Academy later announced that the man's wife had decided to quit her post on the board.  

Three members withdrew last week over the issue, but arcane rules that make appointments for life mean that members cannot technically resign, though they stop participating in activities.

Danius said she had made this decision with immediate effect. "The public row and defections from the Academy have raised concerns that the image of the Nobel Prizes and Sweden's reputation abroad could suffer," she said.

"It has already affected the Nobel Prize quite severely and that is quite a big problem."  

The allegations of sexual assault and harassment were made against Jean-Claude Arnault, the husband of Academy member Katarina Frostenson who also stepped down on Thursday. In an emailed comment to Reuters, Arnault's lawyer, BjornHurtig, said his client rejected all allegations against him. "Jean-Claude Arnault rejects all claims of criminal activity and he rejects other allegations that have been made against him," Hurtig said.

State prosecutors opened a preliminary investigation into the incidents, but said last month some parts of the probe had been shelved due to a lack of evidence and the statute of limitations having passed for some of the incidents. However, prosecutors said the investigation related to some incidents was continuing.

The Swedish Academy said in a statement that Frostenson had decided to leave her post "in the hope that the Swedish Academy will survive as an institution.

"The Academy severed ties with Arnault, whom it had helped financially in running a cultural club in Stockholm, in November following the allegations made against him."