From April to June, more than one in four (28.2 per cent) patients did not receive treatment within clinically recommended time frames, which ranges from 10 minutes for triage 2 'emergency' patients to non-urgent patients who should be seen within 120 minutes.

One in 10 of the 96,222 emergency patients with life-threatening conditions including chest pain and severe burns waited almost half an hour, nearly three times longer than the recommended treatment starting time.

AMA NSW president Dr Kean-Seng Lim said hospitals "were never built to cope with these numbers" of patients in emergency.

"Having 1.5 million emergency presentations at this point in the year is something that has simply never happened before," he said.

"Compounding this is that the acuity of illness and injury suffered by patients presenting at emergency is also increasing.

"Both of these factors can be seen in the poorer results in performance measures."

Nepean Hospital had the lowest percentage of patients whose treatment began within the clinically recommended time frame, at 49.1 per cent.

Having 1.5 million emergency presentations at this point in the year is something that has simply never happened before.

Dr Kean-Seng Lim, AMA NSW president

At 12 other hospitals, the percentage of patients who did begin treatment on time decreased by more than 10 percentage points.

At Bankstown-Lidcombe the percentage of emergency patients whose treatment started on time dropped more than 15 percentage points to 53.4 per cent. Mount Druitt's dropped 12.4 percentage points to 63.5 per cent and Liverpool experienced a 10.8 percentage point decrease to 70.5 per cent.

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However, other hospitals improved emergency wait times despite an increase in patients.

The Children’s Hospital at Westmead treated 16,326 patients in the April to June quarter, an increase of 14.1 percentage points year-on-year. Despite the added pressure, the percentage of patients whose treatment started on time increased by 11.6 percentage points to 69 per cent.

Dr Lim said hospital staff were doing a "phenomenal job".

"Our hospitals are under extreme levels of pressure and it’s only getting worse, but NSW still has an enviable record in terms of providing good levels of care," he said.

"There is urgent need for action if people in NSW can expect to continue to receive the levels of care they deserve."