The Queen star wore the black leather shorts during several shows, including Birmingham and Toronto gigs in 1980 - the height of the band's fame.

Mercury died aged 45 in 1991 from AIDS-related complications.

The 28in (71cm) waist shorts get a mention in the band's authorised biography, Queen: As It Began.

In a chapter about Queen breaking America, it says: "Freddie decided to try to shock the audience with his stage outfit for the encore: the shortest, tightest pair of black leather shorts he could find.

"They didn't leave much to the imagination, but no one complained..."

They had originally been bought at the Queen Fan Club Auction in Southport, in 1993.

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Omega auction house said they were bought by an overseas collector.

The lot also included a copy of the book and the original signed letter of authenticity from fan club secretary Jacky Gunn.

In a separate auction later this year, 1500 of Mercury's personal items from his Kensington home will go on sale.

The collection includes previously unseen handwritten working lyrics to Queen's We Are The Champions, a replica of St Edward's Crown and the telephone he kept by his bed.

Items which will be exhibited at Sotheby's from 4 August until 5 September - which would have marked Mercury's 77th birthday.