The Bureau of Health Information quarterly report covering October to December documented NSW Health services during the peak of the Delta outbreak and the emergence of the Omicron variant.
There were 763,257 emergency department attendances and 320,729 ambulance responses, the highest of any October to December quarter since BHI began reporting in 2010.
NSW ambulances responded to almost 9000 of the highest priority cases (Priority 1A) - an increase of 21.3 per cent or more than 1500 responses - compared with the same quarter in 2020.
The spike in triple zero calls for an ambulance lengthened the time it took paramedics to reach patients, particularly in metropolitan areas, the BHI said.
NSW Health said the median response time for Priority 1A cases was 8.8 minutes, within the 10-minute benchmark.
The lower priority one and priority two patients waited an average of 14.1 and 25.1 minutes, respectively.
Opposition health spokesperson Ryan Park said the latest figures reveal a system "under enormous strain".
"If you need emergency care tomorrow, you will wait longer for the ambulance to turn up than you have done in over 10 years," he told reporters on Wednesday.
NSW Health executive director of system information and analytics branch Sharon Smith admitted "the impact of COVID-19 has unfortunately led to delays in some areas".
But Mr Park says the health system has been suffering from some structural ailments for years.
"We had a health and hospital system already at breaking point and under enormous pressure well before COVID arrived," he said.
Australian Paramedics Association NSW president Chris Kastelan said the response time for Priority 1A cases was the slowest on record in the October-December quarter.
"Patients in NSW are waiting longer and longer for an ambulance, and it isn't a temporary blip because of COVID - today's figures map squarely onto a consistent downward trend over five years," Mr Kastelan said.
"NSW deserves better than a government which looks the other way as our system plummets further into crisis."
NSW paramedics went on strike in February and are preparing for more industrial action over staffing and pay, saying they are worked "to the bone".
On Monday paramedics will refuse to move away from rostered stations once on shift for 24 hours.
NSW AMA president Danielle McMullen said it was no surprise there was a sharp increase in emergency department attendances from mid-December when COVID-19 case numbers started to climb.
"Given the elective surgery suspension from August to October, it's also not a surprise to find that wait times for semi-urgent elective surgery were the longest of any quarter since the BHI began reporting in 2010," she said.
Elective surgery waiting lists reached 95,102 at the end of October but were still below the record 101,024 in June 2020, the BHI said.
There were 46,690 elective surgeries during the quarter but at the end of the year there were 10,770 patients who had waited longer than recommended.
