A Canadian permanent resident jailed without charges in Egypt is at risk of suffering a heart attack if the Canadian government does not step in, his family, friends, and supporters say.

Supporters of Khaled Al-Qazzaz wrote an open letter to Stephen Harper on Tuesday, calling for the PM to use the "full power" of his office to intervene.

Al-Qazzaz, a former staffer of ousted Egyptian president Mohamed Morsi, was jailed along with other Morsi supporters last summer. Al-Qazzaz's Canadian wife says he has not been charged with a crime and has been held in jail ever since.

The open letter says Al-Qazzaz has developed numerous health problems as a result of his incarceration, including heat exhaustion, spinal cord compression and symptoms indicating the risk of a heart attack. Al-Qazzaz continues to languish in a maximum security prison, where he's kept in a cell "the size of a broom closet" and forced to endure temperatures "in excess of 45 degrees C," according to the letter.

"He has not been charged with a crime in any court. He has had no trial," the letter says.

Al-Qazzaz's wife, Sarah Attia, said she has not been allowed to see her husband in jail, but has learned through lawyers that his health is deteriorating rapidly.

"Last week, he lost consciousness in his cell due to dehydration and problems with breathing," Attia told reporters at a news conference on Parliament Hill Tuesday. "They found him four hours later and had to revive him."

Attia said her husband has lost mobility in his right arm due to his confinement, and warned his other extremities are also beginning to show some loss of mobility.

"I fear that if this continues, it will result in permanent disability – or worse," she said.

Alex Neve, secretary general of Amnesty International Canada, said Al-Qazzaz has been "largely left to his fate" by the Canadian government.

"Make no mistake: silence on the part of the Canadian government is not neutral," he said at the same news conference.

Neve said Canada's "quiet diplomacy" approach has not been working, and called for the PM to take a stronger stance in his dealings with the current Egyptian government.

Attia acknowledged that the Canadian embassy in Egypt has been supportive, but added that the Egyptian government has denied her requests to see her husband.

"I hope that I can count on the Canadian government to bring an end to our ordeal," she said.

The open letter was signed by a number of Canadian educators, artists, lawyers and activists, including filmmaker John Greyson, who was detained in an Egyptian jail for a month-and-a-half last summer.

Harper did not release a statement on Al-Qazzaz Tuesday, but a representative from the Prime Minister's Office did acknowledge the situation.

"We are aware of the detention of Mr. Al-Qazzaz and while he is not a Canadian citizen, Canadian officials have been in contact with his family," PMO staffer Jason MacDonald told CTVNews.ca by email Tuesday.

Al-Qazzaz is the father of four young children, all born in Canada.