Up to 3500 State Transit bus drivers across Sydney agreed to go without pay and possibly face disciplinary action after they turned off Opal machines for a day in protest against a plan to privatise services.
The drivers from 12 depots are angry at the government's plan to privatise services in the city's innerwest.
Their union also accused the Berejiklian government of bringing forward the closing date for expressions of interest from private operators - a charge rejected by a Transport NSW spokesperson.
Thursday's fare free day meant drivers were docked pay for not selling tickets and could face further consequences after the Industrial Relations Commission made new orders to turn Opal machines back on.
"The drivers are doing this knowing there are penalties to face," Rail, Tram and Bus Union divisional secretary Chris Preston said told AAP.
"The drivers are that angry, they have no trust in their transport minister. They're doing this to show their anger and let's hope someone listens."
The minister condemned Thursday's "illegal" action saying it was disappointing it was happening despite direct orders from the IRC.
"Get out of the way and allow the workforce to get on with the job of delivering services to the people of the innerwest," Andrew Constance told parliament on Thursday.
It comes after bus drivers took last-minute 24-hour strike action two weeks ago, which resulted in two orders handed down from the IRC for them to return to work.
Buses operated as normal on Thursday, but by turning off the Opal machines, commuters were unable to receive real-time travel information about the bus routes online.
Mr Preston apologised to the "high-tech" commuters who rely on travel apps, and said they'd had to "go back to the old school days" of looking up timetables at the bus stands.
RTBU bus division president David Woollams called on Mr Constance to talk the issue out with the drivers and the union.
"Minister Constance, come down and have a chat with us, the community and the drivers and let's sort this out," Mr Woollams told reporters.
