The Postal Workers Union (PWU) is slamming New Zealand Post for running down its own services, and putting posties in the firing line.
NZ Post will be increasing the cost of FastPost delivery by 50 cents from July 1, but mail will be delivered less frequently.
PWU wants NZ Post to scrap the upcoming price increase until the company can offer a better delivery schedule.
It says most people don't know that fast-post letters are no longer being delivered by a priority postie on Saturdays.
President John Maynard says there's a lack of transparency between the company and its customers.
"Union members tell us that NZ Post is still quite happy to take money off people for FastPost without having any idea that the system is being downgraded," he said.
Mr Maynard says more and more companies are heading to privately-owned postal companies for their services because they're cheaper and more reliable.
"We've been upset about this because posties have a very strong public service culture about them, and the way the company operates is crushing the spirit of that culture out of them.
"We've had increasing complaints from customers and frustrations from the union members we have in postal delivery an increasing failures in the company able to meet its obligations".