A planned strike that would see 1200 bus drivers walk off the job all day on Thursday may not go ahead, after the NSW government applied for an emergency hearing in the Industrial Relations Commission on Wednesday night.

The NSW Rail, Tram and Bus Union (RTBU) announced the strike on Wednesday evening as a protest against the government's plan to privatise bus services in the city's south and inner west.

It was due to begin at midnight and last for for 24 hours.

However, Transport for NSW applied for an urgent hearing at the Industrial Relations Commission, which was heard at 8pm on Wednesday. A government spokeswoman said the IRC reviewed the evidence and found the strike to be illegal, ordering the drivers to work as normal.