Fifty Tranzit bus drivers are set to cut their hours in Wellington today.

Up to 50 Hutt Valley bus drivers will strike on Monday over their new work hours, which the union claims can be as much as 14 hours a day.

The Tramways Union, which has 50 contracted drivers on its books that work for bus operator Tranzit in the Hutt Valley, says it had no choice but to strike after its drivers were this week made to work "illegal" shifts.

"This is expected to put further pressure on Wellington's already chaotic public transport system," the union said in a statement.

RNZ The roll out of new buses and bus routes in Wellington is continuing to be controversial with new drivers struggling to run to timetable.

The dispute over drivers' terms and conditions has been ongoing since Tranzit was announced last year as the new operator for 60 per cent of the Wellington region's bus network.

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Stuff revealed earlier this month that bus drivers faced almost 14-hour work days under Wellington's new public transport network, which launched on Sunday.

CAMERON BURNELL/STUFF New double-decker buses pick up passengers at the Wellington Railway Station bus hub.

Driver rosters supplied by the Tramways Union show one weekday shift starts at 5.38am and does not clock off until 7.19pm that night.

The union has warned for some time it would strike if its drivers' rights were not protected. Secretary Kevin O'Sullivan said on Friday that the roster issue was the final straw.

"It's been some time since we've been forced to take industrial action, but our patience has run out and this is the result."

RNZ Another six months was probably needed in order to successfully introduce radical changes to Wellington's bus network, according to the Regional Council.

The union says bus drivers' work hours are in breach of employment regulations, with some rostered on for more than the 14-hour threshold or not getting paid meal breaks they are entitled to.

From Monday, the 50 union drivers in the Hutt Valley will work for eight hours and then go home, O'Sullivan said. There are 115 drivers in the Hutt Valley in total.

He was unable to confirm how many services that would affect, but Monday would be the first day the region's new bus network would be in full swing as students returned from school holidays.

KEVIN STENT/STUFF The Tramways Union says Hutt Valley bus drivers' work hours are in breach of employment regulations, with some rostered on for more than 14-hours and some not getting paid meal breaks they are entitled to.

"The strike will be continuous until we get a collective agreement in place."

How long that took was "up to the company [Tranzit]," O'Sullivan said. "They agreed six weeks ago they would talk with us about this and we haven't heard from them."

Greater Wellington Regional Council chairman Chris Laidlaw said the council – which oversees public transport under the Metlink banner – would not be getting involved in the dispute between Tranzit and the union.

STUFF Frustrated commuters give up and take taxis to work on the first Monday of Wellington's new bus network.

"All I will say is this does the travelling commuter no favours at all. End of story."

Tranzit managing director Paul Snelgrove said the strike was a "trumped up action".

"Everything the union's claimed has been proven to be untrue – our drivers are paid and treated well. That's why we've been in this industry for close to 100 years.

"Our preparations for a busy week starting on Monday have gone really well, and we'll deal with this situation too. But it's a real shame that the union seems intent on punishing commuters."

Tranzit was open to discussing a collective agreement for union members, but would not engage with people who were "scaremongering" or "intimidating" staff, Snelgrove said.

Earlier on Friday, police were called after two members of the union entered the Tranzit depot in Avalon and refused to leave.

Snelgrove said the two men had left by the time police arrived.