Former prime minister Joe Clark stands beside his official portrait following its unveiling Tuesday on Parliament Hill. (Sean Kilpatrick/Canadian Press)

Former Conservative prime minister Joe Clark's official portrait was unveiled Tuesday during a ceremony on Parliament Hill.

Painted by Alberta artist Patrick Douglass Cox, the portrait will join 18 others in the Centre Block's gallery of prime ministers. The likeness shows Clark standing with one hand slightly raised, apparently in mid-conversation.

Clark, who held office from June 1979 to March 1980, had resisted having his portrait hung in the gallery in the hall outside the House of Commons until he ended his political career. He retired in 2004.

"Hanging is so final," Clark joked during the unveiling.

His wife of almost 35 years, Maureen McTeer, attended the ceremony, as well as his daughter, Catherine, her husband and their young daughter. House of Commons Speaker Peter Milliken, Senate Speaker Noel Kinsella and Senator Marjory LeBreton, Clark's longtime friend and co-worker, paid tribute during the afternoon ceremony.

High-profile politicians were also in the audience of about 100 people, including Liberal Leader Stéphane Dion, Bloc Québécois Leader Gilles Duceppe and former Liberal prime minister Paul Martin.

Prime Minister Stephen Harper wasn't at the unveiling because he is at meetings in Europe. His absence was an exception to a decades-long tradition of a sitting prime minister attending the unveiling of a predecessor's portrait.

The only other prime minister not to attend such a ceremony was Brian Mulroney, who in 1992 missed the unveiling of Pierre Trudeau's portrait. Mulroney was travelling in Western Canada at the time.

Clark said Harper congratulated him personally and by letter.

"No one understands better than I do that international obligations can upset the best-laid plans," said Clark.

Former PM makes appeal for respect

Becoming prime minister was the "defining moment" in his life, said Clark, who said he first came to Parliament Hill in 1957 as part of a Rotary Club program about citizenship.

While he said he didn't want to offer any lessons or words of advice, he did make an appeal for increased respect in government and in the country.

"We are a country of immense diversity. We are going to have our clashes. We have to try to understand the origins, the point of views of others. We have to show them a sense of respect that's based on the sense of worth that they bring," he said, drawing applause from the audience.

Clark became emotional when he thanked his wife, saying she was "as powerful and positive a role model as anyone who sat across the table at [24] Sussex Drive."

Following his stint as prime minister, he served in Mulroney's cabinet, then won the party leadership again after Jean Charest jumped to provincial politics in 1998. Clark sat in Parliament until the 2004 election.

According to the Parliament of Canada, the portraits of former prime ministers are seen by more than 400,000 visitors annually.