The Beach Boys' Brian Wilson (right), who jokes with Lennon

The recording takes the form of a simultaneous telephone interview in which the two groups tease, according to Dave Gioia, a spokesman for the firm auctioning the disc.

The Beach Boys' Brian Wilson jokes with John Lennon about the Beatles' famous haircuts and dress sense.

'Mutual fans'

The groups also discuss the Fab Four's upcoming, untitled film - which became the pop classic A Hard Day's Night.

"It's interesting because the interview was recorded at the height of their fame, and the Beatles and the Beach Boys were big mutual fans of each other's music, as different as they were," said Mr Gioia, representing auctioneers Collectors Universe Inc.

The Beatles have become the most collectable group of all

"It's an extraordinary recording in which the Beatles and the Beach Boys poke fun at each other, in the most good-natured way.

"It's fun to listen to, it's a real stitch," said Mr Gioia.

A music fan spotted the 33 rpm record with its type-written label in a box at a well-known flea market in Newport Beach and paid $5 for it.

The disc, made to help promote a Hollywood event, has now attracted on-line bids of up to $7,050.

Bids close on Wednesday.