About 1000 St John ambulance officers have given notice they'll take industrial action in two weeks' time.

They will still respond to call-outs but the ban on paperwork will stop St John invoicing patients.

Photo: RNZ / Claire Eastham-Farrelly

First Union said the ambulance workers were so exhausted it was dangerous, and this was a reaction to their employer trying to squeeze more out of them.

Most of St John's paramedics were in the union and the action would cover the whole country, it said.

St John human resources director Tom Dodd said it had already agreed to mediation with the five unions who represented staff, before today's notice was issued.

"We continue to work in good faith and discuss relevant issues directly with unions and our staff," he said in a statement.

First Union spokesperson Lynette Blacklaws said the main sticking points were a wage increase offer of 1 percent, and St John wanting to claw back the only remaining penal rate, of time-and-a-half, for working on a scheduled day off.

"Taking a stand is the most responsible thing we can do," she said.

"We are seeking solutions to issues that cause dangerous fatigue such as not receiving rest and meal breaks coupled with an increased workload."

Ms Blacklaws said paramedics often worked 14-hour days.

"It's not safe. It's not safe for the patients, it's not safe for the paramedic. Just very very tired paramedics at the wheel of a bus that's coming to potentially try and save your life."

She said she expected the ban on paperwork to cost St John hundreds of thousands of dollars in lost invoicing.

The last time paramedics took action was about four years ago, over similar issues, Ms Blacklaws said, and St John needed to pressure the government for more funding.

The notice comes on the eve of the junior doctors' two-day strike, which begins at 7am tomorrow.