Hilton is due to start her sentence on 5 June

Time off for good behaviour and prison overcrowding could mean Hilton spends just three weeks in jail.

"It's possible it could be 21 days, 23 days," said Los Angeles County sheriff spokesman Steve Whitmore.

Hilton, 26, was sentenced to 45 days in jail after breaking her probation for a drink-driving conviction. She is due to start her sentence on 5 June.

Mr Whitmore said the exact time she will serve will not be determined until Hilton is checked into the women-only Century Regional Detention Centre in California next month.

He said "our jail is bursting at the seams" and that some female inmates had been released after only serving 10 per cent of their sentence.

But he added that Hilton would not receive any favours just because she is famous.

Hilton supporters think the jail sentence is too harsh

"She will be treated like any other low-level security risk," he said.

Hilton's publicist was not immediately available for comment.

The heiress turned pop singer has said she is "ready to face the consequences" for violating her probation.

In a statement released by her new lawyer, she said: "I do not expect to be treated better than anyone else who violated probation."

She added: "However, my hope is that I will not be treated worse."

The star of reality TV show The Simple Life said she released the statement to clarify matters with the public. "After reading the media's coverage of my court hearing I feel the need to correct what I believe are misperceptions about me," she said.

"I absolutely realise how serious driving under the influence is. I could not live with myself if anyone was injured or killed while I was driving while impaired.

"Clearly, no-one should - no matter how slightly."

But her lawyers have said they will appeal against the sentence and supporters have set up an online petition campaigning for a pardon from the prison sentence, attracting over 20,000 signatures.