Michael Jackson has reportedly asked Britney Spears and Justin Timberlake to join him on stage for some of the dates at his sell-out O2 concerts.

The star is said to be concerned that the performances could lose their "wow factor" due to the length of his 50-date residency, thelondonpaper reports.

An insider said: "Michael knows that stretching out all those shows and keeping it fresh is going to be hard, and one way to do this is to collaborate with some other big stars that he admires.

"The idea would be for them to do five dates each with him. As well as Britney and Justin, he's in talks with producer Timbaland about doing some of the dates too."