Hundreds of New Zealand Blood Service workers walked off the job on Friday afternoon, demanding pay parity with their Health New Zealand colleagues.
New Zealand Blood Service scientist Esperanza Stuart said they provide an essential service.
"Our colleagues at Te Whatu Ora are being paid up to 35% more than us and we want to be paid too. We want fair pay."
The service collects and processes blood products and other tissue from donors, and ensures the donations are safe for use.
The Blood Service has warned hospitals there's a significant risk to the country's blood supply over King's Birthday Weekend and beyond.
Their action coincides with a two-day strike by Junior Doctors, which has forced hundreds of operations to be postponed.
"We'll see what this strike brings us, but we hope no more. We hope that after this Te Whatu Ora and NZBS can figure this out and find somehow to pay us what we're worth."
Friday's four-hour strike by Blood Service workers is part of three weeks of rolling industrial action, with employees planning a full 24-hour strike next Tuesday.
- By Geoff Sloan, made with the support of NZ On Air
