Sydney bus drivers say they will stay on strike for 24 hours despite the Industrial Relations Commission ordering them back to work.
About 1200 drivers walked off the job on Thursday in protest over the NSW government's plan to privatise services in the city's inner west and south.
The stoppage, which began at midnight, affects four depots in Leichhardt, Burwood, Kingsgrove and Tempe.
The Industrial Relations Commission late on Wednesday ordered the drivers not to strike or face "legal consequences".
But Rail, Tram and Bus Union divisional president David Woollams says the drivers remain committed to the stoppage.
"Physically, it would be too big of a job for us to try and physically ring everyone to get them to come back to work," he told AAP on Thursday.
"Even if that was to be the case, the members of these four depots are adamant they are not coming back to work today."
At a meeting of its members RTBU divisional secretary, Chris Preston, apologised for any inconvenience caused by the strike.
"I apologise for the inconvenience to the community in the inner west and the southern region and any other community inconvenienced by the action today," he said.
"This action is on (NSW Transport Minister Andrew) Constance's head."
Responding to the commission's orders, Mr Preston told members to return to work at the meeting but those members present shouted "No".
"I've asked you to go back to work. I've complied with the order," Mr Preston said.