A state-owned French art museum has discovered that more than half of its collection consists of worthless fakes and experts fear that other public galleries may also be stuffed with forgeries.

An art historian raised the alarm after noticing that paintings attributed to Etienne Terrus showed buildings that were only constructed after the artist’s death in 1922.

Experts confirmed that 82 of the 140 works displayed at the Terrus museum in Elne, the artist’s birthplace in southern France, were fakes.

Many of the forged oil paintings, watercolours and drawings were bought with £140,000 of municipal funds over the past few decades. Others were given to the museum by two local groups that raised money to buy them by appealing for donations. Some were bequeathed by a private collector.

Yves Barniol, the mayor of Elne, near the Spanish border, said: “It’s a catastrophe. I put myself in the place of all the people who came to visit the museum, who saw fake works of art, who paid an entrance fee. It’s intolerable and I hope we find those responsible.”