About 100 members of the New Zealand Nurses Organisation will go on strike for a day next month.
Their negotiations for a collective agreement with the Family Planning Association have broken down.
The members - who include nurses, community health promoters and medical administration staff - rejected the association's latest offer because it didn't address wage inequity.
Chris Wilson of the Nurses Organisation said Family Planning needed more funding from the government, but members shouldn't suffer as a result.
"It certainly is a difficult situation for Family Planning, that's recognised.
"But our members have said that it's not appropriate for them to be propping up that valuable service," Ms Wilson said.
The two parties have been in negotiations since March and attended mediation in August.
Ms Wilson said they've been told Family Planning simply doesn't have the funding and would go into an operational deficit if it accepted the demands.
The Nurses Organisation said their members are earning 6 percent less than people in a comparable role with a district health board, and want that gap closed.
They also want the entry level pay bracket for some staff increased to a level even with the living wage.