The 24-hour walkout planned for Monday will affect bus services across most of Greater Sydney including Sutherland Shire, the Hawkesbury area, Western Sydney and the Blue Mountains, as well as some regional services in Newcastle, the Hunter region, the Central Coast, Wollongong and the Illawarra.

The action is being planned by the Transport Workers Union and the Rail, Tram and Bus Union NSW, who said workers from three privately owned companies will walk off the job, including Transit Systems, Transdev and ComfortDelGro.

Bus staff had worked tirelessly through the COVID-19 pandemic and the government must take on the responsibility of looking after drivers despite privatising the industry, TWU state secretary Richard Olsen said.

He said the unions understood the inconvenience of a strike, but believed the community would realise bus drivers had been left with no option.

The top priority of Transport for NSW was to ensure the impact to customers was minimised, a Transport for NSW spokesperson told AAP.

"The health and safety of our customers and our bus drivers is our top priority," the spokesperson said.

"We understand this is a frustrating situation for our customers, and we are doing what we can to reduce disruption during this time."

The spokesperson said bus workers and the operators were continuing negotiations about their enterprise bargaining agreements.

Drivers flagged possible industrial action in February this year if Transport NSW did not take their concerns seriously, and said the decision to take action had come after being ignored.

"The NSW government control(s) the purse strings," Mr Olsen said.

Central to the drivers' demands were same-job same-pay protections, with some drivers currently paid substantially less than others operating the same routes.

A similar wage discrepancy was evident among RTBU members, creating a two-tier workforce, RTBU Tram and Bus Division secretary David Babineau said.

"The state government could put a stop to this by simply coming to the table and committing to fixing the mess that they've created," he said.

Drivers also had questions over safety at work and the welfare of passengers, while many struggled to find break rooms and bathrooms during their shift.

"Drivers are expected to 'hold on' because toilet facilities are either closed or non-existent," Mr Olsen said.

Bus workers called off a strike in 2020 after the government agreed to a request to mandate masks on public transport.

Unions also called for community consultation about the privatisation of bus services.

Australian Associated Press