Union E tū says hospital support staff are facing a wait of several months for an agreed pay increase.

The agreed 2.5% pay increase and $1000 lump sum payment would not reach workers' pockets until the end of January next year.

Meanwhile, Health New Zealand said it had a backlog of collective agreements it was working to implement.

E tū director Finn O'Dwyer-Cunliffe told RNZ staff had expected to see the pay increase in their pockets before Christmas.

"It's a tough pill to swallow for some of the lowest-paid workers in the public health system in New Zealand."

He said some of the support staff were earning below the Living Wage, which was currently $29.90 per hour.

"These aren't highly paid people. They're working really demanding roles, critical roles that keep our hospitals safe, clean, and keep our patients fed. They need the money now."

RNZ understands union members voted for a pay rise and came to an agreement in negotiations on September 3, while the Food and Service Workers collective agreement was signed on October 27.

Health NZ acting executive national director Deborah Kent said the payroll team was working to schedule the implementation of about 34 collective agreements between now and March next year.

"Our payroll teams across New Zealand will be working through the upcoming holiday season to continue to get the collective agreements implemented as soon as practicable."

She said the timeline for support staff pay increases was consistent with commitments made during bargaining with the union.

"Health New Zealand acknowledge the work of our hospital support staff and the valuable contribution they make to hospital operations."