Victoria Beckham is pictured before the start of the Italian Serie A soccer match between AC Milan and Juventus at the San Siro stadium in Milan May 10, 2009. Credit: Reuters/Alessandro Garofalo

I object to celebrities sticking their toe in and stepping out again, like Victoria Beckham, Sienna Miller's sister -- they'll be here for a couple of seasons and then they're off and we're still hanging around, he told reporters backstage after his opening show at London Fashion Week.

She (Beckham) should be happy enough living with David Beckham -- or maybe not, but stop competing with us struggling fashion designers, he said with a laugh.

Celebrity fashion endorsement has long been a powerful marketing tool, prompting the more ambitious to draw up their own designs, often with mixed success.

Beckham, a former Spice Girl, has won over many of her critics since launching her label. Her 1940s, femme fatale-inspired fourth collection, shown during New York Fashion Week, was well received, with newspapers reporting her collections have sold out even during the depths of the financial crisis.

Sienna Miller and her sister Savannah are behind label Twenty8Twelve, which will present its collection Sunday.