Pressure on Victoria's health system shows no sign of easing after the ambulance service experienced one of its busiest periods on record and the number of patients waiting more than 24 hours in emergency departments doubled.

There was a 5.5 per cent jump in demand for ambulances from April to June 2023, compared with the previous three months, making it the third-busiest quarter since records began.

The average wait time for code 1 emergencies across the state was 16.4 minutes, outside the target of under 15 minutes.

Victorian Ambulance Union secretary Danny Hill hit out at the jump, saying the situation was unnecessarily busy.

"Ambulance Victoria and (the Emergency Services Telecommunications Authority) are coding so many cases as code 1, when they don't need to be," Mr Hill told AAP.

He said it meant paramedics were responding to many cases with lights and sirens that weren't emergencies.

Mr Hill said the telecommunications authority, which fields triple zero calls, was doing little to bring down code 1 cases and response times were expected to deteriorate before they improved.

Ambulance Victoria executive Anthony Carlyon said the number of calls requiring a 'lights and sirens' response jumped 29.3 per cent over five years and urged people to only call triple zero in an emergency.

Ambulance Services Minister Gabrielle Williams said she was "optimistic" response times would eventually return to pre-pandemic levels

The squeeze on the system was also felt in hospitals, where 3567 patients had to wait more than 24 hours in emergency departments from April to June.

That's more than double from 12 months ago but just below the end of winter in 2022, according to data released by the Victorian Agency for Health Information.

The number of people on the elective surgery wait list bucked the trend, dropping to just over 72,000 patients - down from almost 86,000 in the same quarter last year.

Australasian College for Emergency Medicine Victoria chair Belinda Hibble said the target for people waiting more than a day in emergency was zero as it could be dangerous.

"Long waits for care also increase delays and risk for all patients and add pressure to staff who are already working beyond their capacity to manage the large number of people requiring complex care," Dr Hibble said.

Health Minister Mary-Anne Thomas attributed emergency department pressures to the "long tail" of the pandemic and said more than two million people had gone to hospital in need of urgent care in 2022-2023.

"We've never had this number of people present to our emergency departments in the past and people are seen based on their acuity and their complexity, the most life-threatening cases will always be seen first," Ms Thomas told reporters.

Opposition health spokeswoman Georgie Crozier said the health system was in crisis.

"These figures are not where it should be," Ms Crozier said.

"Daniel Andrews said three months ago that he was turning it around, in fact these figures demonstrate that things are only getting worse."