The postal service in New Zealand is to cut its deliveries, as customers turn increasingly to electronic communication.

From June 2015, New Zealand Post will make as few as three deliveries a week in urban areas.

John Tulloch from NZ Post has told Pacific Beat there's been a 30 per cent decline in the volume of letters delivered since 2006.

He says the postal service needs the flexibility to remain viable.

"Parcel volumes have grown - that's been fed a lot by e-tailing," he said.

"But we're a volume business in our postal business - whilst parcel volumes have gone up three million in the past six years, letter volumes have gone down 322 million.

"So those numbers don't add up."

Services in rural areas, which tend to rely more on mail, will be maintained at five days.

The changes also allow NZ Post to replace postal workers with self-service kiosks around the country from 2015.

Mr Tulloch says postal operators around the world are facing the same challenges.

"The Internet was there ten years ago...what happened in the mid-2000s [was that] it became a lot more accessible and cheaper," he said.

"The next large wave of technology has been the growth of smartphone technology.

"People are communicating, buying and paying their bills through different channels, and that's a fact of life."

The NZ Government has agreed to the changes to NZ Post's Deed of Understanding.

New Zealand's Engineering, Printing and Manufacturing Union has called the agreement "shocking".