The group says Concession A25, the company that controls the Highway 25 bridge, misleads users about its service fees.
When drivers register as members of Concession A25, they are charged $1.84 or $2.44 each time they cross, depending on the time of day. It costs non-members an extra $5 to cross the bridge.
L'Union des consommateurs spokesman Philippe Viel said drivers don't realize how much they're paying because signs on the bridge are not clear.
"Right now you cannot find the total amount on their signs before crossing the bridge," said Viel.
Tens of thousands of cars cross the bridge everyday. An electronic registering system scans the cars and charges drivers automatically.
Viel said some drivers would have chosen a different route if they had known how much they were going to be charged. He is hoping to reclaim $10 for every crossing, $5 as repayment and $5 as a penalty to the company.
A spokesperson for Concession A25 said the company would not speak to the CBC.