Ambulances in Western Australia are having their defibrillators replaced amid mounting concerns from paramedics.

Media investigations have revealed the current defibrillator in use in 168 ambulances - known as MRx - have a history of safety problems.

The device was removed from sale 18 months ago.

WA’s St John Ambulance says there is a spare defibrillator in each ambulance, but paramedics say the backup is far too basic as it does not provide vital information that an advanced life support defibrillator provides.

Some paramedics have told the ABC that they believe replacing the MRx is stalling an equally needed switch from manual to electric stretchers.

Manual stretchers are reportedly the single greatest contributors to workplace injury to WA paramedics.

WA Health Minister Roger Cook issued a statement saying service provider St John Ambulance must maintain its own equipment “in a manner consistent with providing the services and achieving the service standards”.

“The McGowan government expects St John Ambulance to ensure that patient and worker safety is a priority,” Mr Cook said.

“I have asked St John Ambulance to provide my office with an urgent briefing on the status of the HeartSmart MRx device.”

St John Ambulance had $17.5 million in retained profits in 2017.