Canada’s rejection of BHP’s bid for PotashCorp raises the question of what rules now apply to foreign investors in what has hitherto been one of the world’s most welcoming countries.

Tony Clement, the industry minister, has promised to give reasons for his ruling when it becomes final in early December.

But business leaders agree that the Conservative government needs to clarify the definition of “net benefit” that foreign investors are required to demonstrate under the Investment Canada Act. “Was [the BHP bid] a failure to offer enough by way of collateral benefits or does the size of the asset put it into a dimension that makes it off limits?” asked John Manley, head of the Canadian Council of Chief Executives, whose members have been deeply split on the PotashCorp deal.