Investigators had tried to serve Lutfi with the order for three weeks

Sam Lutfi must not come within 250 yards (228 metres) of the singer until 17 March, US District Court Judge Philip Gutierrez said.

In papers requesting the order three weeks ago, Ms Spears' mother Lynne claimed Mr Lutfi had drugged the star, cut her home phone and yelled at her.

Earlier this week, Ms Spears was denied access to her two young sons.

The singer has not seen her children since 3 January, when she became agitated and was taken to hospital at the end of a court-monitored visit with them.

Ms Spears, who recently spent six days in a psychiatric unit, has repeatedly asked the court to reinstate her visitation rights, but her requests were rejected.

Her father, James Spears, has been granted "temporary conservatorship" over his 26-year-old daughter's life and her estate, thought to be worth $100m (�50.8m).

Conservatorships are generally granted for people deemed to be unable to care for themselves or their affairs.

A lawyer for Mr Spears wrote in court papers that it had taken three weeks to serve the restraining order on Mr Lutfi, who was "apparently evading service".

The order means Mr Lutfi must not contact Ms Spears in any way and must stay away from the homes of her parents and her siblings.

Mr Spears has also been granted permission to sack his daughter's business manager, Howard Grossman.