LOS ANGELES - A court commissioner has warned Britney Spears, in the midst of a child custody dispute with ex-husband Kevin Federline, that she has not been in "substantial compliance" with a previous court order and her visits with her children must be monitored.

In an order released Thursday, Superior Court Commissioner Scott M. Gordon granted some visitation rights to the 25-year-old pop singer. But he required that a monitor must watch her while she is with her sons, two-year-old Sean Preston and one-year-old Jayden James.

The visits will be cut short if the monitor decides any behaviour or action by Spears endangers the children. Following a closed-door hearing Wednesday that Federline attended, a court spokesman indicated Spears would be allowed visits every other day.

Phone messages left for lawyers representing Spears and Federline were not immediately returned Thursday.

Earlier this week, Federline received temporary custody of the children.

Spears turned the boys over to Federline after she failed to produce a California driver's licence and allegedly missed a drug and alcohol test as ordered by the court, her lawyer, Sorrell Trope, told People magazine.

Although a temporary driver's licence was issued to Spears late Tuesday in Santa Monica, Gordon said in his order that she "was not in substantial compliance with material provisions" of his previous ruling.

Gordon also said if Spears misses or refuses a drug and alcohol test, it will be "deemed by the court as a failed test." He also said Spears must complete at least three individual counselling sessions by the next hearing on Oct. 26.

He previously ordered Spears to undergo random drug and alcohol testing twice a week after the court found she engages in "habitual, frequent and continuous use of controlled substances and alcohol."

Gordon also previously ordered Spears to meet weekly with a "parenting coach" who was to report back to the court about her skills. Both Spears and Federline must complete the court's "Parenting Without Conflict" class.

Spears and Federline also were ordered to refrain from drinking or using drugs either in the presence of their children or within 12 hours before taking charge of them.

Federline's attorney, Mark Vincent Kaplan, said Wednesday his client has been in full compliance with the commissioner's order.

Spears and Federline were married in October 2004. She filed for divorce last November and it became official in July. They previously shared custody of the boys. Federline, 29, also has a son and daughter with former girlfriend Shar Jackson.

Spears has spiralled seemingly out of control since splitting with Federline. First she hit the Hollywood party circuit, where she was photographed several times without underwear. Then she volleyed in and out of rehab, shaved her head, beat a car with an umbrella and eventually spent a month at the posh Promises rehab clinic in Malibu.

An MTV Video Music Awards performance intended as a comeback was panned, with Spears appearing lethargic. The following week, her management firm dropped her and her divorce lawyer resigned.

Her problems continued when she was charged with misdemeanour counts of hit-and-run and driving without a valid license for allegedly crashing into a parked car in August.

On the upside, her new song, "Gimme More," topped Billboard's Hot Digital Songs with 179,000 downloads, and jumped from No. 68 to No. 3 on Billboard's Hot 100.

The song is the first single from her new album, set for release Nov. 13.