The Rail, Tram and Bus Union (RTBU) has apologised for today's strike in Newcastle but says the action is necessary to achieve "reasonable" pay for bus drivers.

Members working on bus routes operated by Keolis Downer have started a 24-hour strike action after a breakdown in pay negotiations.

About 150 Hunter bus routes were not in service, including school runs, disrupting the morning commute for students and workers.

"I apologise to the public. This is action that the members don't take lightly," said union spokesman Daniel Jaggers.

"As we've seen, inflation and the cost of fuel has gone through the roof. Groceries are starting to cost a lot more than they used to.

Commuter reaction mixed

The RTBU is pushing for a 7 per cent pay increase over two years for bus drivers, which local commuter David said was "a bit unreasonable".

"I understand the cost-of-living pressures and stuff like that, but the rest of us in private enterprises are having to struggle along without big pay increases," he said.

David walked from the Junction to Newcastle Interchange to get a train after realising there were no buses and said the strike had caused a "really big inconvenience".

Commuter Kathy supported the strike but said a 5 per cent pay rise would be more realistic.

"All the essential workers, like bus drivers, cleaners, aged care and nurses have not have pay rises for quite some time," she said.

"These people work all sorts of hours and weekends and stuff and I think they deserve to be heard."

Keolis Downer said Monday's strike was disappointing for those who relied on Newcastle buses, and encouraged the union to resolve the dispute through discussions rather than industrial action.

The private operator said it would continue to negotiate in good faith to reach an outcome.

Newcastle Light Rail and ferries were running as normal.