Britney Spears' husband Kevin Federline is secretly planning a romantic duet with his ex, it has been claimed.

Kevin - who married Britney in 2004 - has been reportedly visiting former love Shar Jackson and plans to record a song with her.

A source told America's Star magazine: "Kevin hasn't told Britney about it. When she finds out, I think she will go ballistic. I think it could be the last straw."

The pair are said to be keen to record a new version of Bobby Brown's hit love song 'Get Away'.

Even though his musical plans could cause more problems for his marriage, Kevin seems determined to pursue his musical ambitions.

The source claimed: "Kevin doesn't seem to care. He said, 'So I'm going to record a song with Shar. Big deal'."

Britney, however - who is pregnant with the couple's second child - plans to record a duet with Kevin according to Harper's Bazaar.

She told the magazine: "I can't wait to return to performing, but I want to do it right.

"I'm so proud of Kevin. He's been working so hard on his own album since I got pregnant with Sean Preston. I'm so lucky - he's a doll." (Source:BANG Media International)