Discontent over the unreliability of PRESTO technology on the TTC is increasing in Toronto political circles as persistent issues with malfunctioning card readers continue to plague the rollout.

According to the Toronto Sun, Councillor Denzil Minnan-Wong declared the smart card system a "lemon" at yesterday's TTC board meeting, bemoaning the fact that the city is stuck with what he characterizes as a "system that doesn't work."

The conversation took place around a motion to develop a formula for calculating how much revenue the TTC is losing to broken PRESTO readers put forward by Councillor Joe Mihevc.

At the meeting, TTC Deputy CEO Chris Upfold noted that eight to 10 per cent of single PRESTO card readers are still malfunctioning at any given time on TTC vehicles, but new failures are down to one per cent.

There's a significant backlog in trying to update the broken readers, which keeps the overall rate of failure high, even though new problems have been reduced.

For its part, Metrolinx has noted that its goal is to achieve 99 per cent reliability across the system.

The TTC voted in favour of determining exactly how much it's owed for the broken readers, though no one is expecting a huge chunk of cash to come in. Only 10 per cent of TTC rides are taken using a PRESTO card at present.