By Solarina Ho

TORONTO (Reuters) - Edward Snowden, the fugitive former U.S. spy agency contractor who leaked details of mass U.S. surveillance programs, said on Wednesday he is not being offered a fair trial if he returns to the United States.

"I would love to go back and face a fair trial, but unfortunately ... there is no fair trial available, on offer right now," he said from Russia in a live question and answer discussion organized by Canadian Journalists for Free Expression, Toronto's Ryerson University and the Canadian Broadcasting Corp.

"I've been working exhaustively with the government now since I left to try to find terms of a trial," he said.

On Tuesday, his Russian lawyer had said that Snowden has been working with American and German lawyers on a way to return to the United States.

During Wednesday's discussion, in which he took questions via Twitter and from a Toronto audience, Snowden said Canada falls well below other Western nations in the level of oversight it puts on its spy agencies.

"Canadian intelligence has one of the weakest oversight frameworks out of any Western intelligence agency in the world," he said.

He did not comment specifically on new legislation proposed by Canada's Conservative government that would expand the powers of the Canadian Security Intelligence Service, the country's main intelligence service. Critics say the new bill provides little to no additional oversight.

In January, CBC News and news website The Intercept reported that 2012 documents sourced from Snowden showed that Canada's electronic spy agency, the Communications Security Establishment, had intercepted and analyzed up to 15 million file downloads a day.

The Canadian media advocacy group that co-hosted Wednesday's event also launched an archive of all previously published documents released by media outlets working with Snowden.

(Additional reporting and writing by Alastair Sharp; Editing by Chris Reese and Peter Galloway)