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.

"I’m not happy about any of these events," Federline’s attorney Mark Vincent Kaplan said when he left a closed-door emergency hearing on Friday afternoon. "There’s no winners here."

Mr Kaplan said Federline was not in court for the hearing.

The 26-year-old pop star remains in hospital.

Her latest troubles began late 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 officer Ana Aguirre. Early police reports said officers thought Spears might have been under the influence of some substance but Ms Aguirre said there was no evidence of that..

Britney in hospital after row - Jan 4 2008
Troubled Britney Spears is in hospital after adding a new chapter to her troubled life.

The 26-year-old former singer had to be taken from her Los Angeles home by ambulance after police were called to a row between her and ex-husband Kevin Federline over custody of her sons.

Britney finally handed over the boys Sean Preston and Jayden James after three hours during which six police cars, two ambulances and fire engine were sent to the gated community where she lives.

She was taken to Cedars-Sinai Medical Centre but a spokeswoman there refused to comment on her condition.

Police said officers were called to Spears’ house around 8pm on Thursday.

Britney turned the children over around 10.50pm, said officer Jason Lee.

The officer said Britney was under the influence of an unknown substance, but declined to give further details. No injuries were reported.

Britney and Kevin, who were married in October 2004 and divorced in July, have been involved in a long and very public custody battle over their children. Kevin has temporary custody of the children because Britney has defied court orders.

Britney has appeared increasingly out of control the last year. She shaved her head, beat a car with an umbrella and spent a month in rehab and has had a handful of minor car bumps, including one in which she ran over a photographer’s foot.

Earlier on Thursday, Britney appeared for a deposition in her custody dispute, but spent just 14 minutes in court.

Britney lifted into ambulance - Jan 4 2008
Police were called to Britney Spears’s home in a custody dispute that lasted nearly three hours before the singer reportedly turned over her children to ex-husband Kevin Federline.

Aerial TV footage showed Britney, 26, being lifted into an ambulance. It was unclear where she was being taken.

Police said she was under the influence of an unknown substance, and no injuries were reported.

The incident involved a family dispute that officers worked to resolve "peacefully by court order," said a police spokesman.

Six police cars, an ambulance and a fire service vehicle entered Spears’s home in a gated community at around 10.30pm local time (6.30am UK time).

Britney and Kevin are fighting over custody of their sons, two-year-old Sean Preston and one-year-old Jayden James.

Kevin, 29, has temporary custody of the children because Britney, who has limited visitation rights, has defied court orders. The two were married in October 2004 and divorced last July.

Yesterday, the singer appeared for a deposition in the custody dispute.