Ontario's animal welfare agency has notified the provincial government that it will no longer investigate and enforce animal cruelty laws.

In a letter Monday to Community Safety Minister Sylvia Jones, the Ontario Society for the Prevention of Cruelty to Animals said it will not sign a new contract with the province after the current one expires at the end of March.

"The current model is just simply not working," CEO Kate MacDonald told The Canadian Press in an interview. "This is a very significant shift in who we are and what we do."

The letter, obtained by The Canadian Press, said the OSPCA will offer a three-month transition phase, by way of contract, until June 28.

"During the transition period, we will not be accepting complaints or cases dealing with livestock," said the letter signed by MacDonald and Catherine MacNeill, the chair of the OSPCA's board of directors.

MacDonald said the organization will shift into a support role in animal cruelty investigations, providing animal shelter, forensic evidence collection and veterinary services.

The organization has police powers -- it can enforce both provincial and Criminal Code animal cruelty laws -- under the OSPCA Act that became law in 1919.

Its role came into question in early January when an Ontario court found the OSPCA's powers to be unconstitutional and gave the government a year to remedy the situation. The judge said the province erred when it gave police powers to a private organization without imposing accountability and transparency standards on the agency.

The province appealed the decision.

MacDonald said the court's ruling was the "catalyst" in its move away from animal cruelty investigations.

"The recent decision has helped us to see, truly, that enforcement is a function of government," she said.

MacDonald said the agency's 65 enforcement officers will be offered jobs on the organization's expanding animal rescue arm.

The minister of community safety was not immediately available for comment.