Jackson's brother Jermaine, who organised the show, said that they had been unable to perform at the event.

The show was due to take place in Vienna at the at the Schoenbrunn castle at the end of this month but will now be held in London in June 2010.

Jermaine said: "Numerous stars were just not able to change their schedules to make a live appearance at the Vienna event possible."

Representatives for Mary J Blige, Chris Brown and Natalie Cole said none of them would be at the concert, as previously announced.

Jermaine added: "Many artists and performers who I have spoken to personally told me that it would be a great honour to be part of this memorial concert for my late brother.

"However, due to the short time frame it was not possible for many of them to change their schedule so that they could be on stage in Vienna on 26 September, therefore we decided, after careful consideration, to change the date of the tribute concert to June 2010 - just a few weeks before the first anniversary of his untimely death.

"Now we have eight months to put this monumental show together and not just eight weeks."

The organisers, World Tribute Productions, said ticket holders for the Vienna concert would receive a refund and they hoped the rescheduled gig could take place at London's Wembley stadium.