The Rail, Tram and Bus Union said government figures obtained from an FOI request showed commuters have paid an extra $31 million over the last 18 months.

This covered more than 11.5 million trips and the union claimed this was the result of faulty Opal card readers or commuters failing to tap off at the end of their trip.

“The Opal system was riddled problems from day one,” the union’s Chris Preston said.

“On buses commuters are daily being overcharged on as the card readers are riddled with faults or people simply forget to tap off.

“The Baird Government must immediately repay up to $31 million dollars it’s swindled from commuters through its fault ridden Opal system.”

The government figures also showed that refunds were given in less than one per cent – 109,491  – of the 11.5 million trips.

Commuters who forget to tap off at the end of their journey are charged a default fare which is the maximum fare for the mode of transport used.

Transport for NSW was contacted for comment but did not respond before deadline.