The reminiscences of a former prime minister who witnessed the emotional flag debates of the 1960s helped mark the 50th anniversary of the distinctive red-and-white emblem.

Jean Chrétien joined Liberal Leader Justin Trudeau on Sunday to celebrate the milestone, sharing his insight into the political climate that led to the Canadian flag's inception.

"Fifty years ago today it was cold. But if it was cold outside – because it was very cold on Parliament Hill – our hearts were very warm with pride as a new Canadian flag was raised for the first time," he said to hundreds of people at the University of Toronto campus in Mississauga.

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"I was there ... when those who had voted for the flag got up to sing O Canada and unfortunately they were booed," he said, adding that he saw MPs pushing and shoving each other after the vote.

Still, for Mr. Chrétien – then a young MP, almost three decades away from leading the country – it was "a great day" of emancipation for Canada.

Mr. Trudeau spoke about the historical significance of the flag and the difficulties former prime minister Lester B. Pearson faced in making the bold new design a reality.

Mr. Chrétien said the maple-leaf pennant has come to be a symbol of Canadian values.

"It is a flag that represents hope, represents generosity, represents sharing, represents trust," he said. "We should all be grateful to Lester B. Pearson to have the courage to move."

Mr. Chrétien also slipped in a couple of jabs at the current Conservative government as he tied the flag to Canada's international reputation. "It was a time that Canada was respected," he said. "We were showing the world what it was to build a modern society with the diversity that we had."

But "something happened" to Canada's global image in recent years, Mr. Chrétien said, pointing to Prime Minister Stephen Harper's failure to secure Canada a seat on the United Nations security council.

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"I was not very happy that day," Mr. Chrétien said.

The original flag flown over the Peace Tower on Feb. 15, 1965, was never given away.

It's part of the House of Commons heritage collection and is on public display in Parliament's Hall of Honour until March 1.

Mr. Harper said Sunday he would present 50 Canadian flags to 50 Canadians and organizations in recognition of their contributions to the country.

"The Canadian flag is a symbol of the values of peace, democracy, freedom and justice that define and unite us as Canadians," he said in a statement.

"It is a common rallying point for great moments in our country's history and a testament to our ingenuity and achievements, both at home and on the international stage."

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Gov. Gen. David Johnston also marked the anniversary Sunday by unveiling a commemorative coin and stamp in Ottawa's Confederation Park.

"The national flag of Canada is so embedded in our national life and so emblematic of our national purpose that we simply cannot imagine our country without it," Mr. Johnston said in a statement. "It stands for the people we are, the values we cherish and the land we call home."

Mr. Johnston also passed along some words from the Queen.

"On this, the 50th anniversary of the National Flag of Canada, I am pleased to join with all Canadians in the celebration of this unique and cherished symbol of our country and identity," she said.

The Canadian Press