Crude oil prices may be falling, but pump prices continue to hover, in part owing to higher wholesale margins and the weakening Canadian dollar, according to Liberal MP Dan McTeague.

In his online gasoline-price report, McTeague, who represents the Ontario riding of Pickering-Scarborough East, calls current pump prices "unjustifiably high."

"Today's gas price decrease continues to see less of a decrease proportional to the drop in crude oil and NYMEX gasoline," he says in the report. NYMEX is the New York Mercantile Exchange, a venue for commodities trading.

"The effect of a weakening Canadian dollar accounts for some of this, but the ability of Toronto marketers to pad their wholesale margins have increased three cents per litre the past few weeks alone, and the increase in retail margins by 1.5 cents explains the remainder."

The national average price for a litre of gasoline on Tuesday reached $1.307, down from $1.396 a month ago, according to the price tracking website Gasbuddy.com. Light sweet crude hit $114.40 a barrel in trading on Tuesday.

Meanwhile, Petro-Canada filling stations in Alberta and British Columbia were reporting supply is running short because of a technical glitch at the company's refinery in Edmonton.

"Our customers will likely notice some of our sites will run out of gasoline temporarily. Gasoline is still being delivered, but there will be, for Petro-Canada customers, an inconvenience factor," Petro-Canada spokesman Jon Hamilton said.

"The gasoline will be available at other Petro-Canada sites. It just might not be available where you normally fill up."

Statistics Canada on Friday reported a 3.4 per cent year-over-year decline in sales of refined petroleum products in June, owing to weaker demand for gasoline and diesel fuel oil.

With files from the Canadian Press