Michael Pitfield, a former senator and clerk of the Privy Council, has died at the age of 80.

Prime Minister Justin Trudeau announced the death late Thursday, saying Pitfield was a "family friend who was especially dear" to his father and his family.

Pitfield, who joined the public service in 1959, was a close confidant of former prime minister Pierre Trudeau during his time in office.

In addition to his role as a powerful clerk of the Privy Council, Pitfield also served as secretary to the cabinet and as a senator for Ottawa-Vanier over a career spanning 50 years.

'A pivotal role'

Trudeau said Pitfield remains the youngest ever Canadian to lead the public service and called his contributions to Canadian public life "far-reaching and enduring."

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As the winds blow Prime Minister Pierre Trudeau's hair, Queen Elizabeth signs Canada's constitutional proclamation in Ottawa in 1982. The men leaning over the Queen to ensure that the document does not blow away include Michael Pitfield, left. (The Canadian Press)

Pitfield joined the Senate in 1982 and sat as an independent until his retirement in 2010.

"Michael played a pivotal role in the patriation of the Constitution and the establishment of the Canadian Charter of Rights and Freedoms," said Trudeau.

"He was a tireless advocate of bilingualism and national unity whose leadership helped bring us closer as a country and make our democracy uniquely our own."

"On behalf of all Canadians, Sophie and I offer our deepest condolences to his three children, Caroline, Tom, and Kate, and to all of Michael's family and friends," Trudeau added.