An art buyer is suing the defunct Knoedler Gallery, accusing it of selling $37 million in forged paintings.

The buyer, John Howard, alleged yesterday in a civil-racketeering complaint that he paid $4 million in 2007 for a painting that Ann Freedman, the gallery’s president, said was done in the 1950s by Willem de Kooning. Howard alleges the painting was a forgery done by a Freedman associate.

The Upper East Side gallery closed last year after 165 years in business.

Knoedler employees allegedly misrepresented the ownership history of the painting, falsely claimed experts had authenticated the work and sold it to Howard for more than five times what the gallery paid.