Convinced that her ex-husband Kevin Federline, who currently has primary physical custody of their two young children, has been smoking pot around them, pop singer Britney Spears wants to submit them for drug testing in order to prove her point.

Fighting back in the ongoing custody battle with K-Fed for their toddler sons, Sean Preston and Jayden James, Britney suggested Kevin might be smoking marijuana in front of them, and is determined to take measures, Life & Style magazine reported.

"Britney believes Kevin’s been smoking pot in front of the kids" a source reportedly said, adding that "She says she can smell it in the boys’ hair and on their clothes when she has her visitation with them."

"She’s asked the court-appointed monitor and her lawyers if they can prove the kids have been exposed to environments in which drugs have been taken."

While the custody agreement between the two will maintain until February, the "Gimme More" singer will also get a sample from Kevin’s hair if that will increase her chances to regain the custody she left in early October.

Drug expert Marty Brenner confirmed that a sample of hair can provide results can be found with prompt drug testing on hair.

He told Life & Style, "Testing for secondhand marijuana use can be done using a lock of hair. The test must be done within a day or two after exposure. Secondhand smoke would definitely show up, and results usually come back in a couple of days."

If Britney will get permission to use the drug tests as evidence in court, and if the results will come in positive, Federilne would be in danger of losing the custody custody.

Back in October, extras on the North Carolina set of Federline's TV show "One Tree Hill" reportedly complained of him smoking drugs at work.

"He is smoking marijuana all round the set, like it is just part of his lifestyle," New York Daily News quoted a source as saying.

However, a friend of K-Fed’s dismissed Britney’s allegations claiming that although he smokes a lot of pot, he never does it around the children.