About 200 bus drivers from Auckland and Waikato are set to walk off the job tomorrow but Wellington bus drivers will now strike on Thursday.
It was announced last week that Wellington bus companies Tranzurban and Uzabus would begin an indefinite strike tomorrow, after the Tramways Union said they had no options left.
However, the Tramways Union said the decision was made late last night to postpone the strike to Thursday after they received legal advice.
But strikes will go ahead in Auckland and the Waikato after First Union announced overnight that 100 Pavlovich and Ritchies Murphy bus drivers in Auckland would strike tomorrow for 24 hours, starting at 4am.
A further 100 Go Bus drivers in the Waikato will strike from 5am to 9am.
First Union spokesperson Jared Abbott said the measure was part of a long, drawn-out dispute about pay.
"It's been a continuous process, we've been bargaining with these companies for upwards of two years - you see all the other bus operators have reached settlements except for these two companies that seem intent on squeezing more and more profit out of the public service system," he said.
"In Auckland you've got the lowest-paying operators that just aren't willing to pay the market rate - and to be fair, they're not even paying a living wage yet.
"[In Hamilton] We've still got people on just over $17 an hour doing a very important service and we just don't think it's right."
He said while the strikes in the different regions were unrelated, they all stemmed from a common issue.
"These are all the result of the PTOM tendering system which requires councils to tender for the lowest paying operators. Now we've seen that system go through and basically drive the wages and conditions of bus drivers down across the country and this is really the flow-on effect from that.
"It's only logical that it's going to end up in industrial action."
Auckland Transport said around 350 trips will be affected by the strike. The following bus routes will be affected: 66, 111, 112, 114, 131, 132, 133, 134, 138, 141, 142, 143, 146, 152, 154, 33, 362, 365, 368, 371, 372, 373, 376, 377, 378.
It said school buses, trains and ferries would run as normal.
Go Bus chief operating officer Nigel Piper said Hamilton bus passengers were being needlessly inconvenienced.
"We are not surprised by the short notice strike, but we are disappointed that Hamilton bus services have become targets for national action.
"We are currently in a facilitated bargaining process with First Union, which we have put a significant amount of effort into, it's difficult to see the same commitment from the Union."
Mr Piper said the strike action would only affect urban services in Hamilton and Go Bus was trying to minimise disruption.