While not entirely shocking, the allegations are tricky for Sheriff Lee Baca, who had vowed that Hilton would be handled like any other female inmate after she was jailed for violating probation on a drunken driving charge. It raises wider questions about preferential treatment for the wellheeled.

It is alleged, for example, that Hilton was allowed to use a mobile phone at the detention centre while everyone else is expected to stand in line for payphones. Other supposed perks included receiving a new prison uniform instead of a laundered one as would have been more usual, and having her post delivered by prison officers instead of other inmates.

"We're going to investigate it and get to the bottom of it and find out exactly what happened, " promised Steve Whitmore, spokes-man for Baca.

He said the claims had come from deputies in the sheriff 's department.

The case has been trouble for Baca from the start. It was his decision to release the 26year-old on still unspecified medical grounds after she had served only three days, and send her instead into home detention in her Hollywood Hills mansion. A furious judge overruled him the next day and she was returned in tears to her cell amid wide publicity.

Baca has more broadly campaigned for the power to send short-term inmates into home confinement on the grounds of chronic overcrowding in the LA jail system. Specifically in the case of Hilton, he has publicly contended that she received a harsher sentence than she should have done for her driving misdemeanour.

As for Hilton, she was unsurprisingly keeping her counsel yesterday, making no comment either about the perks she is supposed to have received or indeed about the nature of the so-called medical difficulties that led Baca to send her home, if only for one night.

In a post-incarceration interview with Larry King on CNN news, Hilton, who spent most of her sentence in a cell isolated from other inmates, merely indicated that she had suffered from claustrophobia.