Ontario drivers pulling up to the pump can expect a sticker shock, after gas prices made their biggest overnight increase in more than two years.

Across Toronto, the price for regular unleaded gasoline is hovering around an average of 112 cents a litre.

Other major cities across the country did not see the same overnight price jump. Vancouver saw a 1.5-cent jump to 120.8 centres a litre, while Calgary and Winnipeg stayed constant at averages of 96.9 and 95.9 cents a litre respectively.

The average price in Montreal actually fell by 1.5 cents to 116.4 cents a litre.

But gas stations in cities across Ontario were playing the same tune as those in Toronto; Barrie, Hamilton and Ottawa all saw 4.4-cent increases overnight.

Kingston saw a jump of 11 cents a litre, launching the average price to 109.6 cents a litre.

In Toronto, drivers who filled up before midnight paid an average of 108 cents a litre Wednesday night. A few hours later, the price was up to 120.8 cents a litre.

A year ago, the average price was around 98 cents a litre.

According to Liberal MP and gas price guru Dan McTeague, the record overnight hike "has nothing to do with market forces as much of the increase for oil and gasoline" prices on the New York Mercantile Exchange.

"In fact, of the 4.4 cpl (cents per litre) increase, only .5 cpl is attributable to the market," McTeague wrote on his blog, linking the balance of the increase to profit-taking, limited supply and lack of competition at the refinery level.

McTeague, who maintains the popular price-watching website "Tomorrow's Gas Price Today," has predicted that drivers could be paying as much as 120 cents a litre by Christmas, one of the busiest travel times of the year.

The gas industry has consistently denied allegations of price fixing. BNN's Michael Kane told CTV News Channel, "in the case of the oil industry, market forces set the price."

But Kane said understanding how those forces arrive at a price is a "mug's game."

What we do know, Kane explained, is that "gas station operators get a communication from their company's central office that tells them what the gas price should be on the sign outside."

According to a weekly report by Kent Marketing Service on gas prices across the country, the average price in Ontario was 108.9 cents a litre earlier this week.

Quebec's average was the highest with 115.4 cents a litre, while Atlantic Canada saw averages of 111 cents a litre. Western Canada's average gas price was 103.4 cents a litre.

The Canadian average for this week, 108.8 cents a litre, was up from last week's 106.8 cents. The highest average price of the year came three weeks ago, when Canada pump prices averaged 110.1 cents per litre.

McTeague's Tomorrow's Gas Price Today site warns that based on current trends, the price should go up again Thursday night.