The supposedly original artwork included signed lithographs that investors claim in a lawsuit are merely worthless "glorified posters," The Detroit News reported Monday.

The suit, filed in Oakland Circuit Court, alleges the artwork was purchased from Park West Galleries in Southfield, Mich. The investors claim much of the art was purchased by "unsophisticated" collectors during champagne auctions on cruise ships, the newspaper said.

The gallery boasts $300 million in annual revenue and about 300,000 sales a year, and denies the allegations.

"For over 40 years, Park West has serviced 1.2 million clients in gallery sales and sea auctions and stand behind the authenticity of everything we sell, including the works of art in this meritless lawsuit," Park West attorney Rodger Young told the News. "The allegations are easy to make and hard to prove, and we look forward to going before a Michigan jury."