The Union representing transit workers in Canada's most densely populated city called on the province to intervene and identify what it described as a harmful system designed to replace existing monthly transit cards.
December marks the past month that travelers in Toronto will be able to use Metropasses at TTC as the network of buses, trams and subways passes to the Presto map.
But the Amalgam Transit Union, Local 113, sent a letter to Ontario's Doug Ford, urging the government to take immediate action to ensure a smooth transition.
The Union says TTC will not be able to handle Presto users as card readers regularly fail and take too long to repair.
But Anne Marie Aikins, a spokesman for Metrolinx, who runs the throne, says the reliability of card readers for buses and trams is between 98 and 99% every week.
Aikins says the agency is "confident" that Presto can cope with the transition from Metropasses.