Event promoter Georg Kindel and Jackson's brother Jermaine told reporters that too many top performers had scheduling conflicts, and they blamed the media for stirring up a negative atmosphere.
Last Friday's announcement came at the end of a turbulent week of reports that supposedly confirmed that artistes including Mary J. Blige, Chris Brown and Natalie Cole couldn't make the event. Many invited artistes had scheduling issues, and "maybe we underestimated these issues," Kindel said.
"The purpose of this show is to give something back to the fans ... we have to do this right," Jermaine Jackson said, at one point using a tissue to dab at one of his eyes.
"It's not about name-dropping," he added, answering critics who had complained that mega stars such as Madonna didn't figure among the headliners.
Michael Jackson died June 25 in Los Angeles at age 50.
original plan
The original plan had been to stage the tribute on September 26 outside a 17th-century palace in Vienna. Instead, Kindel said, it will be held at London's Wembley Stadium some time in the first half of June 2010.
Everyone who bought tickets for the scuttled Vienna event will get refunds, he said.
Some fans had paid up to €512 (US$745) for VIP seats, and many expressed unhappiness that no major stars had been confirmed. Among the other performers said to have been confirmed were Sister Sledge, Akon and German boy band US5.
Nina Ellend, spokeswoman for World Tribute Productions GmbH, said the issue of whether people would be reimbursed for travel arrangements had not yet been addressed. Roughly 32,500 tickets - half the number available - had been sold, she said.
comeback tour
Kindel told reporters the decision to move the event out of Vienna was made partly because "renowned artistes of the tribute were disrespectfully treated as B-list artistes or even losers".
"We are going to a place where these artistes are greatly appreciated and where Michael Jackson wanted to start his comeback tour," Kindel said.
"We need to be somewhere where this is going to be a wonderful event," Jermaine echoed, adding he was still "very much in love" with the Austrian capital but that he didn't like local speculation about who was coming. He had previously said that Vienna was picked as a venue because his brother "loved castles".
Kindel said tickets to the London concert would go on sale December 1 and begin at £44 (US$73).
The city of Vienna, which considered the tribute a potentially huge tourism boost, had pledged up to €600,000 (US$870,000) to help underwrite the cost of diverting traffic, providing security and producing a promotional video.
But last Friday, deputy mayor Renate Brauner said the city had withdrawn the offer.
"Not a cent will be given to the promoter," public broadcaster ORF quoted her as saying.