The owner of a silkscreen self-portrait of Andy Warhol sued the late artist's estate today, saying it conspired for 20 years to control the market for Warhol's work with authority to stamp "DENIED" on any work it claimed was fake.In a $US20 million ($A23.01 million) lawsuit in US District Court in Manhattan, Joe Simon-Whelan said the Andy Warhol Foundation for the Visual Arts Inc and the Andy Warhol Art Authentication Board force owners of each Warhol work to sign contracts giving them a "perpetual veto right over its authenticity".He accused them of engaging in a two-decade scheme of fraud, collusion and manipulation that caused them to twice deny the authenticity of his 61-by-51-centimetre silkscreen even though it had been authenticated multiple times before by the estate or its related entities.As a result, anyone who buys a Warhol painting that has been authenticated by the board risks having the authenticity revoked at any time, says the lawsuit, which seeks at least $US20 million ($A23.01 million) in damages and class action status.Simon-Whelan, a US film writer and producer who lives in London, accused the foundation and the board of providing "a facade of corporate credibility obscuring a deeply corrupt enterprise that enables defendants to benefit from Warhol's art and reputation".He said they had adopted a policy of rejecting as many works as possible to induce artificial scarcity in the market for Warhol's creations.The foundation's chief financial officer, KC Maurer, said today she had not seen the lawsuit and couldn't comment.Simon-Whelan said he bought the silkscreen, called Double Denied in his court papers, for $US195,000 ($A224,380) in 1989, two years after Warhol died.The work was one of several created in 1964 at Warhol's direction from an acetate personally created and chosen by him, the lawsuit said.It was going to be sold in December 2001 for $US2 million ($A2.3 million) until the authentication board without explanation stamped "DENIED" on the back of it in red ink, which bled through to the front, according to the lawsuit.Simon-Whelan submitted it a second time in 2003 only to get rejected again, the lawsuit said.The lawsuit said Double Denied is one of a small series of paintings created by Warhol so he could exchange them for rare and expensive video cameras, video recorders and other equipment that could be used in his filmmaking.