Martin Lang spent £100,000 (121,000 euros, $163,000) on what he believed was an original work by Russian-born artist Chagall in 1992.
For a BBC TV programme on art forgeries, the painting was tested by experts and sent to the Chagall Committee in Paris for verification.
But Lang, a 63-year-old property developer, was shocked when the committee deemed it to be a fake and told the BBC that under French law it must be destroyed.
The committee has kept the painting - a nude said to date from 1909-1910 - in Paris and will meet on Tuesday to discuss its fate, a spokesman told AFP.
Lang blasted the committee's decision as "draconian".
"I was confused because I couldn't see the logic of destroying something which is possible evidence if forgers were ever caught in the future," he told BBC radio.
"And also, it is basically my property. I just couldn't understand why a committee would be so draconian.
"I believe they intend to destroy it in front of a magistrate.
"It is bizarre.... It is almost vindictive. I do sympathise with the committee -- insofar as you want to do away with forgers and dissuade forgers, but it's not dissuading the forgers, it seems to me you are dissuading honest decent people from coming forward to have their art verified."
Lang said he had written to the committee to propose that they mark the word "forgery" on the back of the painting and return it to him, but is still waiting for a reply.
He said he feared the cost of legal action to force the committee to return the painting would be prohibitive.
"I don't think there is a lot we can do at the moment, we can appeal to their generosity," Lang said.
Chagall, who died in France almost three decades ago, is considered a pioneer of modernism. His work can sell for millions.
The Chagall Committee is run by the artist's grandchildren to protect his reputation in the art world.