The Communications, Energy and Paperworkers Union of Canada has asked the federal government to review retroactively last year's purchase of the former Canwest newspapers under the Investment Canada Act.
The newspaper chain, now called Postmedia, was bought last year by an investment group backed by New York hedge fund Golden Tree Asset Management in a $1.1-billion deal.
The company holds some of Canada's largest daily newspapers including the Vancouver Sun, Vancouver Province, Calgary Herald, Ottawa Citizen, National Post and Montreal Gazette.
Since the purchase, the company has cut about 500 full-time job or roughly nine per cent of its workforce in a bid to reduce costs ahead of an initial public offering later this year.
"This is hardly of net benefit to Canadians, their communities or the critical flow of information in a democratic society," union spokesman Peter Murdoch said.