Britney Spears' one-time love rival Shar Jackson has poked fun at the pop superstar's MTV Video Music Awards disaster in a self-penned rap for a US reality show.

Jackson was pregnant with Kevin Federline's second child when he dumped her for the vivacious Spears.

Jackson was competing in the finals of the MTV show Celebrity Rap Superstar recently when she enjoyed a laugh at the Toxic singer's expense.

Performing as Shar J, Jackson showed off her own rapping skills on the show aired on Thursday last week by cracking: "They should have had me open up at the VMAs," during the song Let It Blow.

The dig comes after Jackson recently revealed she bears no ill will towards her ex, Federline, or his now-ex-wife Spears. She claims Spears stole her then boyfriend, Federline, in 2004.

Jackson and Playboy playmate Kendra Wilkinson, one of Hugh Hefner's three live-in girlfriends, are the finalists of Celebrity Rap Superstar.

The winner of the show will be announced later this week.

Jackson, a former star of TV series Moesha, is hoping to use her appearance on the show to launch her own R&B career.

She has been working with Pharrell Williams on a debut album. - Wenn