Anna Walentynowicz, who as the forefront of the Solidarity movement in its struggle against communist rule, died along alongside Lech Kaczynski, the then Polish president, and 94 others when their plane crashed near Smolensk in western Russia in April 2010.
Since the disaster there have been strong suspicions that Russian authorities failed to indentify the bodies correctly.
Walentynowicz's presumed body was exhumed on Monday and her son Janusz has now said that the remains are "not the body of my mother".
"That's my opinion, and the doctors' opinions all the results of the examination will come later," he said. "But I know what I saw in Moscow, I know my own mother, and the person I saw today on the autopsy table was certainly not the person I recognised as my mother."
Piotr Walentynowicz, Anna's grandson, was also adamant."I do not recognise that body as my grandmother's body," he said.