The Competition Bureau is seeking to block Secure Energy Services Inc. from buying rival Tervita Corp. because of what it says is the deal's potential to drive up prices for industrial waste services in the oil and gas sector.
The two companies operate industrial landfills, treatment and recovery facilities and water disposal wells in Western Canada.
They agreed in March to an all-stock deal that valued Tervita at $478 million when it was announced.
Existing Secure shareholders would own about 52 per cent of the combined company under the proposal.
But the Competition Bureau says it has applied for an order to prevent the companies from closing the deal until the matter is heard by the Competition Tribunal.
The bureau says the proposed deal is likely to result in substantially less competition among waste disposal facilities in the Western Canadian Sedimentary Basin.