The daughter of a former secret service agent claims she has the steel mountaineering instrument, which is stained with the blood of the Russian revolutionary.

Exiled by Joseph Stalin, Trotsky lived a relatively settled life in a leafy suburb of Mexico City until his death in 1940.

Trotsky was always fearful of assassination attempts organised by Stalin. He was finally caught off guard by Ramon Mercader, who on August 20 1940 got access to him on the pretext of needing help.

Once in the study, Mercader struck the creator of the Red Army in the head from behind with the shortened pick he had hidden under his clothes.

Murderer and ice-pick were taken into custody but the weapon later disappeared.

Now Ana Alicia Salas says her father, Commander Alfredo Salas, stole the pick because he wanted to preserve it for posterity.

Trotsky's grandson Seva Volkov, who lived with his grandfather at the time and still lives in Mexico, is willing to provide samples for a DNA test against the blood on the handle only if Salas donates the pick to the museum in the house where the murder took place.

But she said: "I am looking for some financial benefit. I think something as historically important at this should be worth something, no?"