Madonna has agreed to appear on the final of 'The X Factor' - providing certain conditions are met.

The source told the Mail on Sunday newspaper: "Madonna will have been provisionally booked because the final can be subject to change if an artist doesn't approve of the finalists - especially if they have agreed to sing with them.

"Someone like Madonna will want a lot of creative control over her appearance, but for Simon the ratings will be worth it."

What's more, the source revealed that there are certain conditions the 'Like a Virgin' singer must adhere to if she is to appear the show, too.

The insider explained: "She has been told that her label will be expected to pay for any stage props and backing dancers she brings with her."

The proposed appearance could help boost sales of Madonna's next album, which is due to go on sale shortly after the live final.

Meanwhile, another source said: "It had been rumoured that Irish rockers U2 were being lined up to take part. But that has not happened and the confusion may have come because they share the same manager, Guy Oseary."