The families of ethnic Roma, sometimes referred to as the Romany or Gypsies, were forced in 1999 to live in camps built by the United Nations after war broke out a year earlier between Serbia and ethnic Albanian separatists seeking an independent Kosovo. The camps were built on land that was affected by waste from a former lead-smelting factory.

Children under 14 — particularly vulnerable to lead poisoning, which can cause permanent damage to the nervous system and affect brain development — made up approximately half the population of the camps, Mr. Tuncak said. Families complained over many years that the toxic waste was sometimes causing disabilities and possibly fatal illness.

Mr. Tuncak’s criticism came three years after a United Nations human rights panel reviewed the case, and found that the United Nations Interim Administration Mission in Kosovo had acted negligently.

The panel ruled in a 2016 report that the United Nations agency, known as Unmik, “was responsible for compromising irreversibly the life, health and development potential of the complainants that were born and grew as children in the camps.”

Unmik took action to protect United Nations peacekeepers from exposure to lead waste in 2000 but did not take action on behalf of the Roma families in the camps until 2006, Mr. Tuncak said Wednesday.