Greek Prime Minister Kyriakos Mitsotakis on Thursday hit back at accusations that he tried to cover up a sex abuse scandal involving a top theatre director appointed by his government.

Speaking in parliament, Mitsotakis said the opposition and supporting media were dragging public discourse through a "swamp" and spreading "poison".

The debate took place as the former artistic director of Greece's national theatre, Dimitris Lignadis, appeared before a magistrate to answer allegations of raping minors, including migrant children.

Lignadis, 56, resigned on February 6 citing a "toxic climate of rumours, innuendo and leaks". He has been in police custody since the weekend.

On Thursday, he denied ever having sex with minors, and insisted he was not even present during the alleged incidents cited by plaintiffs.

But after hearing from multiple witnesses, a process that lasted all night, the prosecutor and judge agreed to keep Lignadis in custody.

A defence legal argument to the investigating magistrate, leaked to the media, said the case against Lignadis was fabricated by lawyers close to the Greek actors' guild, and that members of the guild board were envious of his success.

Opposition parties have accused the government of dragging its feet in the investigation, which could have led to the destruction of valuable evidence.

Ex-artistic director of Greek National Theatre Dimitris Lignadis is accused of raping minors, including migrant children Ex-artistic director of Greek National Theatre Dimitris Lignadis is accused of raping minors, including migrant children Photo: AFP / LOUISA GOULIAMAKI

Main opposition leader Alexis Tsipras on Thursday told parliament the case amounted to a "major scandal involving an attempted cover-up", accusing the prime minister of hypocrisy and other ministers of lying to the public.

Opposition parties have called for the resignation of Culture Minister Lina Mendoni, whom the prime minister continues to defend.

The Lignadis case is the latest in a belated #MeToo awakening in Greece involving allegations of sexual abuse, harassment and bullying in the fields of arts, sport and education that have rocked the country in recent weeks.

A related judicial inquiry is under way into claims that migrant children had been molested between 2017 and 2018.

The government has promised to introduce a new ethics code to prevent future abuse cases.

"Nobody deserves to live in fear and silence," the PM said Thursday, vowing to introduce tougher sentences for sex crimes.

More than three years after the #MeToo movement surfaced in the United States, the code of silence in Greece was broken last December by a two-time Olympic sailing medallist, Sofia Bekatorou.

Bekatorou said that when she was 21 she was subjected to "sexual harassment and abuse" by a senior federation member in his hotel room, shortly after trials for the 2000 Sydney Olympics.