U.S. National Security Agency whistleblower Edward Snowden says Canada has one of the "weakest oversight" frameworks for intelligence gathering in the Western world.

Snowden made the comments during a teleconference discussion hosted by Canadian Journalists for Free Expression and the Ryerson School of Journalism, moderated by CBC Radio host Anna Maria Tremonti. He was speaking via video link from Russia.

Snowden said he wouldn't specifically weigh in on the government's new anti-terror legislation, saying that whether it is good or bad is ultimately up for Canadians to decide. But he likened it to controversial U.S. laws, calling it "an emulation of the American Patriot Act."

Bill C-51 provides for a sweeping range of measures that would allow suspects to be detained based on less evidence and lets CSIS actively interfere with suspects' travel plans and finances.

Critics say the legislation is too broad and lacks oversight. 

The government, however, says the powers in C-51 are necessary to keep Canadians safe. It points to the requirement for judges to sign off in advance of CSIS breaking Canadian law, arguing that is adequate oversight for the new powers. 

'No fair trial on offer'

Snowden is a controversial figure. The documents he leaked in 2013 revealed the U.S. government has programs in place to spy on almost everything that hundreds of millions of people do online, including emails, social networking posts, online chat histories, phone calls and texts.

Some hail him as a civil rights hero, while others condemn him as a traitor for revealing classified documents and compromising national security. He is wanted by the U.S. government on espionage charges.

Snowden was stranded in a Moscow airport in 2013 on his way from Hong Kong to Cuba, shortly after he released extensive documentation about the NSA surveillance programs. Russia has granted him asylum, attracting the ire of the U.S. 

Snowden said he would be willing to return to the U.S. if he could be guaranteed a fair trial, but said that wasn't possible. He cited the possibility that the government would use secret, classified evidence.

"There is no fair trial available on offer right now," he said. 

'Rare instances of criminal activity'

The documents Snowden leaked to journalists revealed details about the electronic spying agencies of a number of countries, including Canada.

One program operated by the Communication Security Establishment and dubbed Levitation sifts through millions of videos and documents downloaded worldwide, CBC News revealed earlier this year.  

Snowden said the bulk collection of data has fundamentally altered the relationship between citizens and government, and cannot be counted on to stop attacks.

"We cannot throw away all of our rights, all of our liberties, all of our traditions, because we are afraid of rare instances of criminal activity," he said. 

With files from The Associated Press