Starting Monday, the biggest grocery chain in Ontario will start charging shoppers in its Toronto stores for plastic bags.

Customers at Loblaws will have to pay five cents for every plastic bag.

It's part of a plan, according to company officials, that was in the works before Toronto city council started talking about ways to reduce plastic bags.

Andre Iacobucci, Loblaws' executive vice-president, said the company wasn't in favour of another idea that was floated that would have required stores to give customers a 10-cent refund for every bag not used.

"The much more effective encouragement to reduce plastic bag use is to charge a nominal fee rather than give a discount. In our Quebec stores, for example, we have historically given a discount for the use of a reusable bag and our plastic bag use reduction in those stores is in the five to 10 per cent range versus the 55 per cent reduction when you charge [customers] a nominal fee," he said.

Loblaws will begin charging for bags in the rest of the stores across Canada on April 22, Earth Day.

Loblaws vice-president Inge van den Berg expects to reduce plastic bag use by half.

"There are certain municipalities that do recycle them, but unfortunately [plastic bags] are often left to go to landfill sites. And we just want to try to eliminate those so that more are reused, recyled, or in this case, ideally, avoided," he said.

The Toronto bylaw requiring all retail stores in the city to charge five cents for each plastic bag takes effect June 1.