A Los Angeles judge rejected the singer's request to lift a court order which gave her former spouse Kevin Federline sole custody of the children on Monday.
LA superior court commissioner Scott Gordon instead granted Spears, 25, rights to visit Sean Preston, two, and Jayden James, one.
The failure of the singer to regain custody of the youngsters marks the latest setback for the troubled pop princess.
It also comes as reports of a sex tape involving her and a man in Hawaii emerged, with the 28-year-old in question saying he filmed the footage without the pop star's knowledge.
Spears previously shared custody of her sons with her ex-husband and no reason has been given for the legal decision to place them in his care full-time.
However her lawyer Sorrell Trope has told People magazine that the star lost custody of her children because she was unable to show proof of having complied with previous court orders.
In a previous hearing Judge Gordon told Spears that she was a "habitual, frequent and continuous" user of alcohol and controlled substances and ordered her to appear for random drug tests twice a week.
Meanwhile the star was recently charged with misdemeanour hit-and-run, for driving without a valid licence. She could face up to six months in jail and be forced to pay a $1,000 (£500) fine if convicted.
Another hearing has been set for October 26th to review the situation regarding the custody of Spears' sons.
Since splitting with Federline last November Spears' eccentric behaviour has led to a barrage of headlines about her emotional state, while the singer was also dropped by her management last month after a disastrous comeback performance at the MTV video music awards.
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