"Posh" Spice, who is pregnant by her footballer fiance, said the blue Porsche was "the car in which we shared our first kiss together".

The car attracted worldwide interest and was expected to sell for around £100,000, but bidding at Christie's auction house stopped at £65,000.

A percentage of the proceeds was to have been donated to a baby-related charity chosen by the couple.

The car, which is registered in David Beckham's name and has full leather sports seats, electric sun roof and air conditioning, was bought by the Manchester United star in August, 1987, and has just 11,200 miles on the clock.

The Porsche will be sent back to the couple who were not at the auction.

Malcolm Welford, director of International Motor Cars, at Christie's, said: "We are disappointed. They were a very nice couple, very easy to deal with, The car will go back to them and they will decide what to do with it."

The Porsche 911 Carrera S Tiptronic was just one of a number of cars on sale at a prestige motor auction at Christie's, in London.

An assortment of automobile-related literature, artworks and collectors items went under the hammer and the sale as a whole made £1.6m.