He said: "I'm choreographing and set-designing Britney's tour. There has been talk of Madonna making an appearance, and there's so many place we could take that. At this point, the main issue is timing." This would not be the first time Britney and Madonna have appeared on stage together.

They famously locked lips at the 2003 MTV Video Music Awards, and Britney also performed 'Human Nature' with Madonna as part of her 'Sticky and Sweet' world tour last month. It was recently reported Britney's tour, to support her new LP 'Circus', is inspired by her breakdown, and will see the mother-of-two flee to the circus before emerging from the end of a rainbow following a thunderstorm.

A source said: "Britney is well aware of what a roller coaster she has been on. She thought the best metaphor to use would be the circus. Fans get to travel with her through her fall from grace and her eventual rehabilitation."

Britney, 27, famously went off the rails following the end of her marriage to Kevin Federline. She shaved her head in February 2007 and was hospitalised several times - most famously in January of this year when she refused to return sons Sean Preston, three, and Jayden James, two, to their father.

Since then, Britney's dad Jamie has taken on co-conservatorship of her affairs and she has begun to turn her life and career around. 'The Circus Starring Britney Spears' begins in New Orleans on March 3.