Works by French sculptor Stéphane Simon, which show nude, classical-style figures taking selfies, were being displayed in Paris during UNESCO's European Heritage Days event in September.
But officials decided to cover the offending parts of the artworks with underwear, to the shock of Simon and the ridicule of arts commentators.
Simon told CNN the clothing was "disgusting" and said the experience left him "humiliated."
"I felt ashamed, so deeply sad to see all these years of work and research broken," he added. "For two days visitors came to meet, to ask me: 'But why did you do that?' But it was not my choice."
The artworks, part of a project called "In Memory of Me," had been designed to comment on the spread of the selfie in recent years.
"I should have spent two days explaining the fascinating link" between the practice of selfie-taking and Ancient Greek history, Simon added.
He said he had raised the issue of nudity during planning meetings with UNESCO before the event, but had not been asked to cover up the works until a few days before the sculptures were displayed and had no time to amend the pieces appropriately.
A UNESCO spokesman told CNN: "This was due to an unfortunate misunderstanding. Our entire work and mandate is in favor of freedom of creation."
Simon added to CNN that the organization has recognized a "mistake made by one employee."