The union representing the state's ambulance workers has taken the service to the commission over what it says is an overwhelming workload that is putting patients and paramedics at risk.

Figures released to the commission show in the past four years there has been an increase of 30,000 call-outs annually, or 4 per cent.  The average time spent at each call-out has increased by 15 per cent.

Earlier this year Fairfax Media revealed ambulance crews had been left minding patients for up to 20 hours after delays admitting them to hospital.

Yet a document seen by Fairfax Media shows the service says it has not had any discussions with the Minister of Health about increasing staff levels to meet the increasing demand, despite. the Baird government on Tuesday announcing it would be increasing paramedic numbers by 53 if elected.

Greg Bruce, an ambulance councillor with the Health Services Union, said paramedics were more stretched than ever before.

There had been an increase in trauma, and serious events such as heart attacks and strokes, which needed to be taken to specialist centres rather than the nearest hospital.

"We are overwhelmed," he said. "There are constantly dispatchers calling cars and saying 'is anybody clear to do this job?'."

Data provided to the commission shows the average utilisation rate at midday, which shows how many ambulances are busy, increased from 66.5 per cent in 2010 to 81.5 per cent in 2014.

"We treat the person we are with, but you don't know what the next job will be and the person waiting is potentially going to suffer," Mr Bruce said. "It could be an elderly person who has fallen with a fractured hip … who has to just lay there".

The Labor Party has promised to hire 500 extra paramedics if elected, and the HSU is pushing to get the Liberal Party to match the promise.

However, after being ordered by the Industrial Relations Commission to produce any documents it had in which it had sought or discussed further resourcing with the Ministry of Health, the Ambulance Service said no such documents existed.

HSU secretary Gerard Hayes said if this was true the government was not planning for the future.

"We have been trusting it to plan for the state's burgeoning emergency needs" Mr Hayes said. "The response to the IRC shows us it has done no such planning and continues to put the public at risk."

But the Ambulance Service said it was  planning for the future using other methods, including a model of "dynamic deployment" to ensure that "regardless of demand, the nearest available paramedic crew is always responded to patients in need of emergency medical care".

"We constantly assess demand, workload and rostering and manage our staff establishment accordingly to ensure we are best placed to respond to those in need," NSW Ambulance Deputy Commissioner Mike Willis said."Not all patients who call us need an ambulance or to go to hospital."

Health Minister Jillian Skinner said she supported completely the Ambulance Service's strategic planning.

"NSW Ambulance is treating more patients than ever before in better timeframes," she said. "The 2014 Auditor-General's report showed the median response time for all potentially life-threatening cases in NSW has fallen for the first time in five years."

She said Labor's promise to increase paramedic numbers was "undercooked and underfunded".

"Just four years ago it promised to recruit 45paramedics at a cost of $15 million if re-elected, now it says 500 are needed but have costed at only $46 million," she said.
Labor Health spokesman Walt Secord said the costing for the paramedic policy had been done by the independent Parliamentary Budget Office.

"The Liberals and Nationals are only familiar with cutting services rather than adding health professionals and have forgotten how to cost positive policies," he said.