TORONTO - Another major grocery store chain will soon ask shoppers in Ontario and Quebec to spend a nickel for each throwaway plastic bag, a practice that environmentalists believe will soon become the norm at supermarkets nationwide.

Metro Inc. (TSX:MRU.A), which operates nearly 600 stores, is set to announce Tuesday a plan to charge customers a five-cent-per-bag fee.

The fee kicks in June 1 -- the same day the City of Toronto starts forcing stores to charge for single-use bags.

"We started looking at that and decided it made sense to extend that to both provinces," said Selena Fiacco, communications director for Metro Ontario.

"We really want to reduce the number of plastic bags in circulation."

Metro joins Canada's two largest grocery chains, Loblaw Cos. Ltd. (TSX:L) and Sobeys (TSX:EMP.A) in charging five cents per bag. Sobeys, however, only charges the fee in Ontario.

Flat-fee programs have been a staple for years at some stores, such as discount grocer No Frills.

Though Metro's program only affects Ontario and Quebec -- the two provinces where the company has stores -- environmentalists say it's only a matter of time before grocers across Canada start charging for bags.

"I think after the city of Toronto's program is implemented, you'll see it across the board," said Jo-Anne St. Godard, executive director of Recycling Council of Ontario.

"Especially for the national chains, they don't tend to launch programs in by jurisdictions, they tend to do it nationally, it's easier for them," St. Godard said.

The council supports the fees, she added, because it puts a price tag on pollution.

"Plastic bags, typically, are overused and people take for granted. It's also a tough wrap, or package, to have recycled."

Toronto's plastic bag fee bylaw, which takes effect June 1, was the result of a compromise reached in November after a controversial pitch from city hall that would have required retailers to offer a 10-cent-a-bag discount to customers.

Critics described the plan as unworkable and prompted major grocery chains to lobby the city for alternative measures.

Grocers aren't the only retailers trying to curb the use of plastic shopping bags.

The Liquor Control Board of Ontario has banned plastic and only offers paper bags.

In October 2007, furniture retailer IKEA Canada began charging five cents for plastic bags, donating proceeds to Tree Canada to help plant trees throughout the country.

Similarly, Metro is pledging to put some of the money from the sales of both paper and plastic bags towards charity. The company said it will unveil a program to provide $2 million in grants for environmental projects at schools in Ontario and Quebec.

Canadians currently take home about 55 million bags from stores every week.