A Quebec consumer rights group is calling out some of the province's major grocers for failing to respect a law on per unit pricing.

Option Consommateurs surveyed eight major retail outlets where food is sold and found that only one – Costco – respected the law that forces grocers to list how much certain foods cost on a per 100-gram basis.

The other outlets surveyed were Loblaws, IGA, Metro, Walmart, Jean-Coutu, Pharmaprix and Couche-Tard, and Option Consommateurs says Metro and IGA were the worst offenders, though all seven were guilty to varying degrees.

The consumer group says listing prices on a per 100-gram basis makes comparison shopping easier.

The Quebec Food Retailers Association counters that while that may be true for meats and produce, it is not necessarily the case for everything.

"I don't think the consumer has that kind of problem," the association's Florent Gravel said.

Many consumers interviewed by CTV Montreal's Rob Lurie agreed, but some would like to have the details called for by the law.

"I'd like to know exactly what I'm paying for," one shopper said. "I might be overpaying and I don't know it."