Fairfax Media understands one man who was in the most urgent patient category there is - and had been listed as "arrest not breathing" by ambulance responders - took 44 minutes to be assisted and then admitted to Liverpool Hospital. Other seriously ill patients, including one who had had a stroke and was numb down one side of his body and others who were not fully conscious, took more than two hours to be admitted to hospitals including Bankstown, Prince of Wales and Royal Prince Alfred.

The problem is known as "bed block", where ambulances have been forced to line up outside emergency departments because of a lack of beds inside hospitals.

But NSW Health insists that no patients were put at risk by the delays, and those who needed urgent treatment got it.

Fairfax Media has seen multiple examples of ambulances stuck waiting in hospitals across the city on Thursday, in some cases for nearly three hours as they were unable to offload patients.

Paramedics are furious at the delays, which they say put lives at risk because they leave them unable to respond to emergency calls.

This week they started a change.org petition, which is believed to have been signed by more than 1300 serving ambulance officers begging Health Minister Jillian Skinner to increase the resources available to the Ambulance Service.

Labor health spokesman Walt Secord has called on the premier to guarantee that patient safety in NSW has not been compromised.

Mr Secord said it was "absolutely unacceptable for patients to be forced to wait outside emergency departments when treatment is only metres away".

"It is irresponsible for the Liberals and Nationals to allow patients including those with chest pains, stroke paralysis and other emergency medical situations to languish for three hours," he said.

He said the "avalanche" of reports of hospitals unable to admit patients this week and ambulances lined up six deep outside of emergency departments across the state were putting patients at risk.

"In an emergency situation, every minute counts; this puts lives at risk. Paramedics, nurses and doctors are working their guts out, but they are not being properly resourced by the State and Federal Liberal-National governments."

Premier Mike Baird this week argued the GST should be raised to 15 per cent to pay for spiralling health costs.

Health Services Union secretary Gerard Hayes said there were not enough paramedics available to deal with increasing calls, let alone to sit waiting at hospitals.

"This is a crisis that is causing lengthy response times and we are concerned the State Government appears unwilling to address the bed block problem," he said.

But acting health minister Pru Goward said local health districts had measures in place to deal with the extra demand for emergency care during winter.

"More patients are currently presenting to our emergency departments with conditions or illnesses associated with the flu season," she said.

She said the government had increased funding for the ambulance service by 26 per cent since 2010, while the growth in ambulance emergency call-outs in that time had only been half that.

In its second term the government was also planning to spend $5 billion on capital works to fix ageing infrastructure in hospitals.

A spokesman for NSW Health said patients requiring urgent care are always seen first, and within the time-frames recommended by emergency doctors, while those who were assessed on arrival as having less serious conditions would wait longer.

"Despite being busy, NSW Ambulance had available resources to respond to patients," he said. "Emergency Department staff worked closely with their NSW Ambulance colleagues during this period and their hard work is highly commended."

"NSW Ambulance paramedics are highly trained clinicians with the skills to provide patient care for anyone with a life threatening condition."