A scandal over Silvio Berlusconi's relationship with a teenage Moroccan girl took on legal and political overtones today when a senior police officer confirmed that the Italian prime minister's office had intervened on her behalf when she was detained on suspicion of theft, claiming she was the granddaughter of the Egyptian president.

That would appear to leave Berlusconi open to claims that he abused his position – a criminal offence under Italian law.

As further details emerged of claims made by the girl, even long-standing supporters of the prime minister were privately voicing despair at his apparent failure to alter his behaviour after a string of sex scandals last year.

Late yesterday, Berlusconi tried to pull back from his earlier apparent admission that, as "a person with a heart", he had helped the young Moroccan dancer – who calls herself Ruby Rubacuori (Ruby Heartrobber) – when she was taken to a police station in Milan in May.

According to Italian media reports, a showgirl turned politician close to Berlusconi collected Ruby following her release.

The prime minister said he was unaware of any telephone call from his office, but added: "I merely made a telephone call to find someone who could make themselves available for the entrusting of a person who had aroused the sympathy of us all and told a dramatic story to which we gave credit."

Interviewed by the daily La Stampa newspaper, Vincenzo Indolfi, the station commander at the time of the incident, said one of his officers had received a call from the prime minister's office. He said the caller had said "something like: 'Is it true you've detained this person? Then make the [necessary] checks and then see what to do.'"

Indolfi, who has since been promoted to a job in the Italian equivalent of the cabinet office, confirmed media reports that the prime minister's office had claimed Ruby was the granddaughter of the Egyptian president, Hosni Mubarak.

The 17 year-old, whose real name was variously reported as Karima or Rachida, has a colourful Facebook page featuring photos of her wearing basques, latex and a bunny outfit. She lists her interests as belly dancing and Taekwondo.

In interviews published today, she claimed to have visited Berlusconi's villa only once, on Valentine's Day this year. According to Italian media reports, her mobile phone was located by investigators as being within the zone including the villa that night.

Police were said to have a statement from her saying she had been given a car by the prime minister. The statement was taken as part of an investigation into alleged aiding and abetting of prostitution, in which three Berlusconi associates, including the woman who collected Ruby, are suspects.