A rail union plan to shut down the NSW transport network's Opal card readers is set to cost the government about $2 million every day.
The Rail, Tram and Bus Union (RTBU) is pushing ahead with a plan to deactivate the state's Opal readers, preventing commuters tapping on to pay for trips, as part of its ongoing industrial action.
Over the weekend, the union withdrew its original application to switch off the readers after a legal threat from the government - filing a new application on Monday.
Treasurer Matt Kean says shutting off the Opal card readers will deprive the state of funds to pay aggrieved train drivers, with the money needed by the government to fund essential services.
Deactivating the readers on Sydney trains and the metro would cost the government between $1.5m and $2m in lost revenue every day, AAP understands.
The action would cost the government approximately $50m if the shutdown continued for a month.
"My message to the RTBU is stop using the public as your political playthings," Mr Kean told reporters on Tuesday.
"It's got to stop. We will continue to stand up for the people of this state and call out their disgraceful behaviour."
On Monday, RTBU secretary Alex Claassens said he was confident the new filing would be successful.
Premier Dominic Perrottet says the government is poised to react if there is any more industrial action or if commuters are unable to pay for trips.
"If that action is taken, either a further strike which ... inconveniences people across the state, we will seek to terminate that agreement in the Fair Work Commission (FWC)," he told 2GB on Tuesday.
"Any industrial activity taken on the metro system which is costing taxpayers billions, then we will also seek to terminate."
The premier first threatened to terminate the agreement after a month of industrial action in August if there was further action.
The union said it was confident it would prevail and have the readers switched off as it continues its long industrial campaign over the safety of a new intercity train fleet and wages and conditions for workers.
The union believes its new application to switch off the readers will stand up.
"It was just a last-minute desperate bid to try and stop us from locking those gates open and allowing the commuters of NSW to travel for free," Mr Claassens said.
A decision over whether the Opal scanners can be shut down will be made during a hearing in the FWC in the next 24 hours.
If the commission accepts the action, the readers will be switched off 10 days later.