About 1000 St John ambulance workers will have their wages cut for taking a third month of strike action, First Union says.

Photo: ST JOHN NZ

Ambulance officers are entering their third month of strike action after collective agreement negotiations broke down.

As part of the strike, union members have been wearing tops that read "Healthy Ambos Save Lives" instead of their uniform.

In a written statement, St John's clinical operations director Norma Lane said ambulance officers needed to be visible to members of the public and, and other emergency services personnel, to meet health and safety requirements.

She said St John had asked striking staff to wear a high-visibility vest while attending jobs, but First Union did not support the proposal.

Ms Lane said employees who did not wear the vest would receive 10 percent less in their pay packet.

"I can assure you we have not taken this step lightly but do so out of concern for the health and safety of our staff as well as for our patients and other emergency personnel who need to be able to be easily identifiable as ambulance personnel," Ms Lane said.

The statement said employers were entitled to ''make a specified pay deduction from employees' pay for participation in a partial strike'' under the Employment Relations Act of 2000.

First Union transport and logistics secretary Jared Abbott said it was astounding St John would deduct 10 percent of the striking paramedics' pay, when the strike action cost nothing.

Mr Abbott said St John's excuse that the deductions were for health and safety reasons didn't add up, when they forced paramedics to work nine hours without a break, and sent single-crew ambulances to emergencies.