Britney Spears is secretly plotting to flee to Europe with their two boys, The ENQUIRER has learned. Brit plans to kick off her comeback tour in France and then enter a European rehab facility for her booze and drug problems, sources say.

Once she?s settled overseas, the boys will join her. But Kevin fears she?ll simply kidnap the boys ? and he?s hired a private investigator to follow her, insiders say.

?Britney has already asked Kevin if she can take the kids abroad when she tours, and he?s said no,? said a source.

?But Brit knows she?ll never get the treatment she needs unless she gets away from Hollywood ? and she?s said there?s no way she?s going to leave her kids behind!?

Right now the couple is locked into a temporary custody agreement that bars either of them from taking the boys out of Los Angeles County without the other?s permission. Meanwhile Kevin has filed for primary custody ? and pals say he?ll stop at nothing to win full custody.

In fact, he?s already hired a private investigator to follow Britney and document where she takes the boys.

?With all the money and resources available to her, Kevin is paranoid that Britney could try to kidnap the kids,? said the source. ?She?s already dropping hints that she?s going to pack up and leave without telling him.?

Meanwhile, Britney?s legal team is researching extradition issues involving the boys.

?It appears that Kevin cannot force extradition of the boys regardless of any U.S. court decision. It?s going to be Britney?s loophole out of the country,? the insider divulged.

?Publicly, Britney will say that she?ll be out of the country for only six weeks, but she?s secretly planning an extended stay to wait out Kevin?s legal attempts at gaining full custody and to strengthen her negotiating position.

?It seems to be the answer to providing her some distance from her problems, shielding the boys from the custody battle and giving her an opportunity to clean up her act.?