A new scandal is rocking the Vatican as police recently raided a drugs and gay sex party at a cardinal's apartment near the city.

Without revealing the name of the occupant of the apartment, police said that the person is believed to be a priest who serves as a secretary to cardinal Francesco Coccopalmerio, the head of the Pontifical Council for Legislative texts and a personal adviser to Pope Francis.

According to Italian daily Il Fatto Quotidiano which first published the news, police raided the apartment in June after complaints from neighbours who reported unusual behaviour among people visiting the apartment.

The newspaper quoted the police as saying that they found drugs and a group of men engaged in sexual activity when they entered the apartment.

The police have arrested the priest and taken him for questioning, presumably on drugs charges. It is not a criminal offence to engage in private same-sex activity in Vatican City.

The apartment belongs to the Congregation for the Doctrine of the Faith, whose duties include investigating clerical sexual abuse.

Coccopalmerio had reportedly recommended his aide for promotion to bishop, but that consideration may be put on hold following this incident and two previous alleged drug overdoses.

Meanwhile, the Pope is under huge pressure from sex abuse scandals involving Vatican churches, priests and cardinals. The latest are charges of child sex abuse against cardinal George Pell, who will return to Australia to stand trial. The Pope's critics have reportedly blamed him for picking wrong people for key positions.