Auction houses go to war for the right to stage the biggest private-owner sale ever

The fashion designer Yves Saint Laurent amassed an art collection that is renowned as one of the most fabulous in private hands. It includes works by Old Masters and contemporary greats, among them Picasso, Mondrian, Warhol, Matisse and Goya, to name just a few.

Now, following his death last month aged 71, Saint Laurent's business partner, former companion and heir, Pierre Bergé – with whom he built the collection – is reported to be considering a massive international sale.

With the collection believed to be worth a staggering £300m, it would be not only the sale of the century, but the biggest private-owner sale ever.

With the glamour surrounding the YSL brand and the vast sums involved, The Art Newspaper reports that the world's two biggest auction houses, Sotheby's and Christie's, have locked horns over which one should handle the sale.

Both houses have apparently "pitched" to M Bergé, who runs his own small auction house in Paris, which is unable to handle the size of the auction.

The paper claims Sotheby's had all but secured the sale in a deal that fell through a month before the designer's death. Christie's quickly stepped in and is believed to be close to clinching the deal. Christie's is helped by the fact that François Pinault, its owner, owned the YSL couture house before Saint Laurent retired in 2002 and it ceased operating.

One of Saint Laurent's most famous designs was inspired by his love of art: the Mondrian dress, which was part of his 1966 Pop Art collection.

Saint Laurent drew up a will with M Bergé saying that the art collection should either be left to the foundation they had created in Paris to preserve his work, or sold, with the proceeds left to the foundation. Although M Bergé, who was the business brains behind YSL for many years, and Saint Laurent were renowned art collectors, little is known about the details of their collection, though it was described by Sotheby's UK chairman, James Stourton, in his 2007 book Great Collectors of Our Time, as a "room of masterpieces".