Britney Spears feels "betrayed" by Kevin Federline.

The singer is reportedly furious with her ex-husband - with who she has two children, Sean Preston, three, and Jayden James, two - after he proposed to current girlfriend Victoria Prince because she still has feelings for him.

"It wouldn't surprise me if her flirting with other guys was purely to make him jealous."

Britney - who divorced Kevin in 2007 - is said to be particularly concerned with the amount of time Victoria will be spending with her sons.

The source added: "Britney's not keen on Victoria. Victoria gets on really well with Sean and Jayden and sees more of them than Britney because they live with Kevin.

"I don't think Britney saw her as a threat until Kevin proposed but now she will be stepmother to Britney's kids and that doesn't make her happy."