KEVIN FEDERLINE won't let his son Sean Preston join Britney Spears on stage.

The pop princess' ex-husband appears to want to ban his eight-year-old son from performing alongside Britney when she begins her two-year concert residency, 'Piece of Me', at the Planet Hollywood Hotel in Las Vegas this December.

Sean has allegedly developed a taste for the spotlight since joining the singer for her 'Ooh La La' music video, while his younger brother, six-year-old Jayden, is too nervous to take part in the live gigs.

Asked whether he'd let his son perform, Kevin - who was married to Britney from 2004 to 2007 - pointedly said: ''I mean ... we'll see about that, won't we.''

Probed further by a TMZ reporter as to whether he'd like Sean to perform, Kevin quipped: ''Yeah, if he was like 25 years old.''

The star - who wed his long-term girlfriend Victoria Prince earlier this month - has clearly moved on from Britney, and has no plans to watch her rumoured $310,000-a-night performances in the US gambling capital.

He joked: ''Nah man. Not my thing. When I'm in Vegas, I'm at the craps tables.''

Meanwhile, sources claims the 'Toxic' hitmaker hasn't managed to sell out many of the concert dates ahead of the big December 27 kick-off.

A source told ''After spending hundreds of thousands on promo, they expected to instantly sell out all of the first 16 shows, but they didn't come close!

''In fact, Britney only sold out three of the 16 shows put on sale and many are considering this a disaster.''