The Communications, Energy and Paperworkers Union is calling on the prime minister to investigate whether Canwest has fallen under foreign control, citing what it calls ‘serious concerns’ over the influence of the broadcaster’s U.S. partners.

The union says it believes control of the company may have shifted into non-Canadian hands, contrary to federal law, because of Canwest’s current financial troubles.

‘The Canadian government should be monitoring Canwest’s actions to ensure that control is being exercised by Canadians, particularly while this debt-ridden company restructures itself to meet the massive debt it took on,’ said Peter Murdoch, VP of media for CEP, in a statement.

The union raised similar concerns two years ago when Canwest joined with U.S.-based Goldman Sachs in its bid to purchase the Alliance Atlantis channels, though the move was approved by the CRTC.

The CRTC had no comment on CEP’s recent concerns. Calls for comment to the Prime Minister’s Office and Canwest were not returned.

CEP represents over 20,000 media workers, including employees in Canwest’s print and broadcast outlets.