Fahmy's family called on supporters to use the hashtag "HarperCallEgypt" in their efforts to encourage the prime minister to urgently lobby for 40-year-old's release this week.
The initiative came a day after Egyptian authorities announced a date for Fahmy's retrial — a move that shocked him and his family, who had previously been told by then-foreign affairs minister John Baird that his release was "imminent."
The new trial is expected to begin on Thursday and Fahmy's family said they are "extremely worried" that his release could be delayed indefinitely.
"We're just in shock. We don't understand how this happened and why," Fahmy's brother, Adel Fahmy, told The Canadian Press. "Why does my brother have to go through all this torment?"
A spokeswoman for Lynne Yelich, junior minister responsible for consular affairs, said Prime Minister Harper has "personally" raised Fahmy's case with the highest level of the Egyptian leadership.
"We understand this is an upsetting time for the family. We continue to call for Mohamed Fahmy's immediate release," Erica Meekes said in an email.
Among those who have called on Harper to intervene in Fahmy's case is Tarek Loubani, a Canadian doctor who was also jailed in Egypt in 2013 along with his filmmaker colleague, John Greyson.
"I write to you as a Canadian who wants to see my government speak out for a fellow Canadian who is currently in jail in Egypt," Loubani wrote in an email to the prime minister that was obtained by The Canadian Press.
"I also write to you as a former prisoner of the same jail that Fahmy is in now. You got me and John Greyson out of jail through the strong and unequivocal actions of your government. Your words meant something then, and they mean something now."
Loubani and Greyson spent two months behind bars after their arrest and beating during an anti-government protest in Cairo. They both credited Harper and his government for relentlessly pushing for their freedom.
Fahmy, meanwhile, has been behind bars for more than a year.
He and two colleagues — Australian Peter Greste and Egyptian Baher Mohamed — were working for satellite news broadcaster Al Jazeera English when they were arrested on Dec. 29, 2013.
They were accused of supporting the banned Islamist Muslim Brotherhood group of ousted Egyptian president Mohammed Morsi. They were also charged with fabricating footage to undermine Egypt's national security. They denied all the allegations against them.
After a trial that was internationally denounced as a sham, Fahmy and Greste were sentenced to seven years in prison, while Mohamed was sentenced to 10 years.
Following an appeal in January, their case was slated for a retrial — though a date had not been set and Fahmy's family hoped diplomatic efforts would result in a release.
Greste was abruptly freed last Sunday under new legislation that allows Egypt's president to deport foreigners convicted or accused of crimes. Fahmy gave up his dual Egyptian citizenship with the hope of being released under the same legislation, but that hope was diminished by the prospect of Thursday's retrial.
"It means that he cannot be deported, it is in the jurisdiction of the court," Adel Fahmy said. "It means the Canadian government has failed us."
NDP Leader Tom Mulcair said the Australian prime minister "got directly involved" in the case of Fahmy's colleague, Peter Greste.
"The Australian government behaved with the Australian journalist as if they were dealing with an Australian. Mr. Harper has dealt with the Fahmy case all along as if somehow, he wasn't really a Canadian," Mulcair said at an event in Toronto.
Adel Fahmy said his brother has been "going through an emotional roller coaster."
"He's angry. He's just shocked," he said.
Fahmy moved to Canada with his family in 1991, living in Montreal and Vancouver for years before eventually moving abroad for work, which included covering stories for the New York Times and CNN.
He took over as the bureau chief for Al Jazeera's English-language channel in Cairo in September 2013.
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