The son of Gulnara Karimova, the eldest daughter of the late Uzbek leader, has called for her status to be officially recognized.
Karimova, who was once tipped as a potential successor to her father, Islam Karimov, vanished from public life amid a corruption scandal more than two years ago.
In an interview with the BBC, Islam Karimov Jr. said his mother was being held in a "two-to-three room annex" to her main property in Tashkent.
Karimov Jr., who lives in London, accused the Uzbek security services of keeping his mother in isolation, adding that being held incommunicado for such a long time must have affected her health.
"To be isolated for two or three years without any even basic human rights that every person deserves on this earth, I'm sure that any person will need some kind of medical attention," he said. "But mentally she is sane."
When authoritarian President Islam Karimov died in September, neither of the siblings or their mother attended the funeral.
Islam Karimov Jr. said his sister and mother were prevented from going and he himself could not risk the trip back home.
"I wanted to go, but I knew that if I go to the funeral I would not come back," he said. "They need all three of us there to limit our activity and our voices,"