OTTAWA -- The owners of a port and broken rail line in northern Manitoba are filing a complaint against the federal government under the North American Free Trade Agreement.

Denver-based Omnitrax says Ottawa's decision to end the Canadian Wheat Board's monopoly in 2012 drastically cut grain shipments through the Port of Churchill, because they moved to other ports in the open market.

In a notice filed with the federal government today, Omnitrax says the change made the port and rail line to Churchill no longer viable.

The rail line is the only ground connection to the subarctic town and it has been inoperable since it was damaged by severe flooding this spring.

As a result, goods and people have had to be flown into Churchill at much higher cost.

The federal government has served notice it intends to sue Omnitrax for failing to repair and maintain the rail line after receiving $18.8 million for repairs and upgrades a decade ago.

Omnitrax's complaint alleges the end of the wheat board was devastating to Omnitrax and benefited other rail lines and ports, all of which are Canadian-owned.

"Article 1102 of the NAFTA requires that Canada provide to investors or investments of the other NAFTA Parties treatment that is 'no less favourable' than it provides to its own," the notice document states.

"Through the steps it has taken to undercut the (the rail line) and its market position relative to Canadian-owned railways, the Government of Canada has de facto discriminated against Omnitrax to the benefit of its Canadian competitors, so as to provide Omnitrax with treatment less favourable than that accorded to Canadian-owned enterprises in like circumstances."