The Beach Boys' hits include Surfin' USA and California Girls

Cooper Owen, which is handling the sale of the 28 lots, says the vendor bought the items legitimately from a representative of the band.

Managing director John Collins said: "No proof of theft has been offered."

The band, who say US police are investigating their allegations, have threatened to sue Cooper Owen, the vendor and anyone who buys the items.

The band's label Brother Records Inc said in a statement: "The FBI and Interpol may also become involved in the investigation."

Vigorous denial

Mr Collins told the BBC News website that Cooper Owen had been in discussions with the Beach Boys about the theft allegations.

"They have offered no evidence so we have no reason to stop the auction at the moment," he said.

Brian Wilson has been hailed as one of pop's finest songwriters

"The vendor vigorously denies the claims. He is furious as he bought the items at a sale by a Beach Boys representative who was clearing out junk around 25 years ago."

Mr Collins said the auctioneers were consulting lawyers over the future of the sale and possible legal action against the band.

The auction, due to take place on Thursday, includes the Beach Boys' early contracts, lyrics and hand written music sheets.

The lots include the original arrangement sheets for Good Vibrations and God Only Knows, both with handwritten notes by songwriter Brian Wilson.

Rare items

Collectors are being offered Wilson and co-writer Mike Love's contract for the hit Do It Again and personal photographs of the band with late Beatle George Harrison.

Other items up for sale include original test pressings for some of their best known hits including Fun, Fun, Fun and I Get Around.

Asking prices have not been placed on the rarities.