TORONTO - Premier Dalton McGuinty says he "screwed up'' when he said municipalities could have tougher anti-pesticide rules than the province.

In unveiling Ontario's pesticide ban two weeks ago, McGuinty said municipalities would be able to introduce tougher rules if they wanted to.

He now says he was wrong and Environment Minister John Gerretsen -- who was standing next to him at the time -- was "unduly deferential'' when he remained silent about the error.

McGuinty says he's instructed Gerretsen to correct him right away if he ever makes a mistake again in public.

Progressive Conservative Peter Shurman says it's an ongoing problem with McGuinty, who has shown he isn't prepared to answer questions about his government's major plans.

More than 300 pesticide products are expected to be prohibited for use once the Ontario ban on the sale and cosmetic use of pesticides is fully implemented in 2009.