TORONTO - An Ontario court is hearing a challenge Wednesday to endangered species rules that environmental groups argue actually further threaten animals the law is meant to protect.

The groups Ontario Nature and Wildlands League point to a regulation change in 2013 that exempted some industries such as forestry, oil and gas, and mining from a prohibition against killing at-risk species or destroying their habitats.

They say the exemptions remove the Endangered Species Act's core protections for almost all of Ontario's 155 endangered and threatened species.

Lawyers for the environmental groups are arguing at Divisional Court that the minister of natural resources failed to determine if the regulation was likely to adversely affect each endangered species.

Lawyers for the government argue that the minister duly made that determination and that exemptions can only apply when a proponent meets a number of onerous conditions.

The government says the Endangered Species Act has the protection of at-risk species as a central concern, but is balanced with "appropriate social, economic, health and cultural considerations."