Yakov Dzhugashvili, a 33year-old artist living in Stalin's native Georgia, believes his great-grandfather was poisoned in 1953, possibly on the orders of Nikita Khrushchev, who succeeded him. He has written to President Vladimir Putin demanding an investigation, saying those involved in the alleged plot to kill Stalin should be named and the incident classified as a coup.

"We need to find the truth.

Who was involved in this? We need to establish the level of responsibility of everyone who was involved, " he said.

Stalin died on 5 March 1953 after suffering what was described as a brain haemorrhage and a stroke. He was 73.

Several historians have suggested he was killed with a powerful rat poison that causes strokes. Secret police chief Lavrenty Beria is said to have boasted of "taking him out".

Unusually, his guards were sent to bed the night before he suffered the stroke, and the Politburo was strangely slow to grant him medical treatment.

It has been suggested that his underlings wanted him dead because they feared he was intent on going to war with the US, worried they would be swept away in a new wave of purges and wanted to head off a crackdown on Jews he was apparently planning.

Dzhugashvili believes his request will be taken seriously because many Russians hold 'Uncle Joe' in high esteem. His grandfather was Stalin's son Yakov, who was shot escaping from a German prisoner of war camp in 1943 after Stalin rejected an offer to trade him for a German general.