Shar Jackson claims Britney Spears knew she was pregnant when she started dating Kevin Federline

Kevin Federline's ex Shar Jackson has claimed that Britney Spears knew she was pregnant with his child when she started dating the dancer.

In her new memoir, The Woman in Me, the Toxic singer reflected on her early romance with the backup dancer and claimed she was "clueless" about the fact he had a child with the actress and another baby on the way.

Kevin and Shar share two children together: Kori, now 21, and Kaleb, 19. The pair became engaged in 2004 but separated shortly before Kaleb's birth after Kevin met Britney while he was away for a supposed audition for a commercial.

"Then I didn't hear from him for three days," the actress told the outlet. "I later found out they had met at a club on the first night, when he went out with his friends. I felt angry and betrayed and I went numb.

"I went onto autopilot. I felt betrayed and crushed. I thought, 'How could you do something like that?'"

When she saw photos of Britney and Kevin together, she recalled, "For about a day-and-a-half I was in a state of disbelief."

The television personality alleged that Britney knew of her pregnancy before Kaleb's birth and even sat outside the hospital while Kevin was in the delivery room.

Britney and Kevin got married later that year and had two sons, Sean Preston, 18, and Jayden James, 17. The pop star filed for divorce in late 2006.

Shar told the publication she was not surprised the relationship fizzled out.

"I think her relationship with Kevin was a fantasy for both of them," she said. "To me, anything built on a rocky foundation isn't going to last and they started rocky because he was in a relationship."