Prime Minister Stephen Harper's decision not to attend the opening of the 16th International AIDS Conference in Toronto this weekend is drawing criticism from some delegates.

The federal government will be represented at the conference by Health Minister Tony Clement.

Louise Binder, who co-chairs the federal ministerial advisory council on AIDS, said she is disappointed with Harper.

"It's not a political matter for me," she said.

"This is the most serious health problem the globe has ever seen, and we're hosting the largest conference with the most media that's ever been and our prime minister can't come and say a few words of welcome," she said.

Richard Elliott of the Canadian HIV/AIDS Legal Network, an internationally recognized think-tank, shares the same view.

"I think [Harper's decision not to attend] sends a very poor message about the level of commitment of the government of Canada to dealing with this epidemic," he said.

Binder and Elliott say Harper's absence will not go unnoticed when the conference opens Sunday evening, and they've warned the government to expect some backlash.

The 16th edition of the biennial International AIDS Conference runs Aug. 13 to 18. Roughly 20,000 participants, including scientists, health-care providers, political leaders, government and non-governmental officials, media and people living with HIV/AIDS are expected to attend.

This is the third time the conference has been held in Canada. It was held in Montreal in 1989 and in Vancouver in 1996.

In 1989, Prime Minister Brian Mulroney did attend the event in Quebec, but seven years later, Prime Minister Jean Chrétien did not go to Vancouver.