Ontario will uphold Canada's new prostitution law after a review by the province's attorney general found it to be constitutional, Premier Kathleen Wynne said Wednesday.

Wynne issued a statement the day after the law came into effect in December, saying she had a "grave concern" that it would not make sex workers safer, and asked the attorney general to review the law and advise her on the constitutional validity.

The premier said Wednesday that the review found the law to be constitutional so Ontario will be taking no further action "at this point."

"We will uphold the law," the premier said. "We'll obviously monitor and determine the impact of the law, but there's no clear unconstitutionality in the law."

The sweeping new changes to the way prostitution is regulated in Canada follow a Supreme Court decision that found the old laws violated the rights of prostitutes.

Attorney General Madeleine Meilleur said her senior staff concluded that the new law answers concerns that the Supreme Court had about the previous law, but she would not divulge their reasoning.

"The legal opinion that was provided to me is privileged, so I'm not going to express every single detail that was in the legal opinion, but the importance to you is that it's constitutionally sound," she said.

Meilleur said there are approximately 26 cases being prosecuted in Ontario under the new law.

A coalition of sex-trade workers and their supporters said Wednesday the new law, which criminalizes paying for sex, communicating for sex or advertising sex services, is extremely similar to the old one, and called on Ontario to not enforce it.

"(We are) profoundly disappointed that the province appears to be turning its back on sex workers and Ontarian communities, despite Premier Wynne's own 'grave concerns' with the new sex work law," said the group that includes the Sex Professionals of Canada, the Canadian HIV/AIDS Legal Network and the sex-trade workers who launched the original court challenge.

"Sex workers have consistently articulated the many ways in which criminalizing them, their clients and their work settings does nothing to protect them, but instead undermines their ability to control their conditions of work to protect their health and safety. The law ensures that harms to sex workers will continue, and is a terrible step backwards."