The auctioneers behind a huge April sale of Michael Jackson items, including the gates of the singer's Neverland Ranch in California, on Thursday denied claims it did not have permission to sell them.

Jackson's production company MJJ Productions filed a lawsuit in Los Angeles on Wednesday claiming that Julien's Auction House had "effectively stolen Michael Jackson's personal property" and refused to return it.

The news came as the reclusive pop star appeared in London and announced a series of comeback concerts in the British capital in July.

The five-day auction, set for April 21-25 in Beverly Hills, was to feature some 2,000 Jackson items and was expected to fetch up to $3 million.

"The lawsuit came as a total shock to us," auctioneer Darren Julien said on Thursday. "We have worked very closely with Michael Jackson over the last eight months and his manager Dr Tohme, and Dr Tohme has approved everything that we have done."

"They approached us and we have totally cooperated with them as we do with all our clients. If they did not want these items auctioned, why have an auction house come to see them?" he added.

Auction catalogs and pictures of the items for sale, which also include a signature Jackson single white crystal-laden glove, had been shared with, and approved by, Jackson and Tohme before being printed in February, Julien said.

The lawsuit said some of the items had "extraordinary sentimental value" and that Julien's had refused to return them.

Julien, whose company has worked in the past with stars like Cher and Barbra Streisand, said his company had spent hundreds of thousands of dollars preparing the Jackson auction, which was to have been preceded by an exhibit in Beverly Hills. It was unclear if the auction will proceed.

Jackson, 50, once one of the world's biggest pop stars, has been a virtual recluse since his acquittal in 2005 on criminal charges of molesting a young boy.