Earlier, Canada was advised through its charge d'affaires in Tehran to "stay out of our politics," after having raised concerns over post-election tumult in Iran, Cannon told public broadcaster CBC.
"And we will not," he said. "We will continue to promote democracy. We will continue to challenge Iran on human rights.
"There are clear cases of fraud that have been put forward," he continued.
Canada is "extremely concerned by the brutality that is taking place in Iran at this period in time, and we have called upon the Iranians to cease this (violence)," he said.
Cannon also called for a full and "transparent" investigation of Friday's presidential election results.
On Monday, Canada called in Iran's top diplomat in Ottawa to explain the detention of Canadian journalist covering anti-government protests in Tehran.
Toronto's Globe and Mail newspaper said Iranian riot police had arrested one of its freelancers on Sunday, but released him after a few hours, telling him there had been a "terrible misunderstanding."
In Iran, tens of thousands of supporters of opposition candidate Mir Hossein Mousavi demonstrated for a sixth straight day on Thursday, keeping up the pressure on the Islamic regime over the disputed vote, witnesses told AFP.
Iranian state radio has reported seven deaths since the protests started.
