The troubled singer was taken to hospital on Thursday night for psychological tests after refusing to hand over her children to their father.

On Friday, a court commissioner gave sole physical and legal custody of the former couple's two boys to Federline and suspended the troubled singer's visitation rights.

The previous evening, Spears, who has limited visitation rights, had been taken from her home to a hospital by paramedics after police had to intervene when she refused to return the children to Federline after a court-monitored visit.

The singer was yesterday pictured being taken to hospital on a stretcher on which she was restrained by straps. In Spears' absence on Friday, court commissioner Scott Gordon ordered another hearing to be held next week.

Yesterday, Spears' mother Lynne Spears summed up the mounting concern over her daughter's health. "Just say prayers," she told the celebrity news show Access Hollywood.

Federline had previously been awarded temporary custody of two-year-old Sean Preston and one-year-old Jayden James because Spears has defied court orders, resulting in limitations on her visitation.

Federline was also not in court for the Friday hearing but his attorney, Mark Kaplan, said: "I'm not happy about any of these events. There's no winners here."

Lawyers for Spears have filed a court motion begging to be relieved from their contract with the star, saying she is impossible to represent.

Law professor Steve Cron predicted that Spears will face sanctions from the court for her behaviour. "My guess is that she won't be seeing her kids for a while," said Cron, who teaches at Pepperdine University in Malibu.

Commissioner Gordon has little option other than to further reduce the time Spears can legally spend with her children, Cron said. "At least for the time being until she gets some help," he added. "She's obviously a very troubled person."

The latest episode of the 26-year-old pop star's life began at around 8pm on Thursday when officers were called to her home to help resolve a dispute over her refusal to turn the children over to Federline, as dictated by their custody agreement. It took two to three hours to resolve the conflict, said Los Angeles police officer Ana Aguirre. "There was a time where she was within the residence and wasn't available to speak to the officers, apparently," she said. "There was no threat to the children."

Police resolved the conflict, Aguirre said. "Both children were turned over to her ex-husband for custody, and Spears was taken to a local hospital for medical treatment."

Early police reports said officers thought Spears might have been under the influence of a substance, but Aguirre said there was no evidence of that.

Officers at the scene determined that paramedics "needed to be called" but it was unclear why, she said.

The singer wasn't arrested in connection with the custody dispute, Aguirre added. "There was no actual crime that was involved."

Ruth Schreibman, a marriage and family therapist, said Spears "needs an enormous amount of help" to find out why she is behaving erratically.

"Is she bipolar? Is she depressed? Is it postpartum depression? Is it drugs and alcohol? There's just so much attention and it's such an accelerated speed of life that how can there be any normalcy?"

Spears and Federline were married in October 2004. Her life has spiralled downward since their divorce in July. She has been photographed without underwear and appeared to be drunk and out of control in public. She shaved her head, beat a car with an umbrella and spent a month in rehab.

She had hoped to regain her pop crown with a much-hyped performance at MTV's Video Music Awards in September, but it was panned by fans and critics.

Still, Spears' latest album, Blackout, earned positive reviews when it was released in October and brought Spears her first No 1 hit in years, 'Gimme More'.