Gas stations could pay up to $100 million if the court rules in the plaintiffs' favour in a class-action lawsuit expansion over alleged gasoline price-fixing in several major cities in Quebec, said George Iny, head of the Automobile Protection Association, who filed the lawsuit.

On Thursday, Quebec's highest court authorized the lawsuit against Ultramar, Orco, Irving, Couche-Tard, Pétroles Cardin, Pétroles Global and Philippe Gosselin and associates.

The first criminal accusations in June 2008 were made in Sherbrooke, Magog, Victoriaville and Thetford Mines after an investigation by the competition bureau.

The expansion, filed by Daniel Thouin and the Automobile Protection Association, takes aim at 23 additional markets.

According to the plaintiffs, businesses were contacting each other and collectively hiking prices.

Iny said the lawsuit was broadened based on evidence uncovered by an independent researcher.

"His conclusion is that in many markets, the prices for all three grades of gasoline were identical even though the markets were not next to one another. So, as a consequence, [the researcher] says it's impossible that pure chance [...] would result in the exact same prices over the exact same days over a period of six months," Iny said.

If the suit turns in favour of the plaintiffs, gas stations could have to pay out as much as $100 million, he said.

The suit against the big oil companies covers motorists who filled up between January 2002 and June 2006 in Quebec City, Trois-Rivières and other major cities.

To date, 27 people and seven businesses have pleaded guilty.

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