Paramedics across NSW have launched a 12-hour strike, defying orders made by the state's Industrial Relations Commission.
Members of the Australian Paramedics Association in NSW will attend emergency "lights and sirens" jobs but will limit other responses from 7am on Friday as part of an ongoing pay dispute.
The commission late on Thursday ruled the action by the smaller of the state's two paramedic unions would not be protected, with the threatened strike also condemned by the rival Health Services Union.
Despite government legal efforts to halt the action, however, the association says its members remain determined.
"This strike symbolises our unyielding quest for justice," president Brett Simpson said in a statement on Friday morning.
"We want to assure the public that emergencies will still be attended to, with our focus intensifying on life-threatening cases.
"Our decision to limit responses to non-emergency jobs enhances our capacity to manage critical cases."
The union says more than 90 per cent of its members voted to support the strike.
"Facing potential legal repercussions and a substantial fine of up to $20,000 per day, our commitment remains firm," Mr Simpson said.
"This fight is about our paramedics' welfare and the quality of healthcare for everyone in NSW."
The union says NSW paramedics are the lowest paid in the country, with staff not only suffering financially but experiencing a draining of skilled professionals to other states.
Opposition health spokesman Matt Kean said the Labor government had promised a pay increase for paramedics ahead of the election and now the "chickens are coming home to roost".
"Paramedics deserve to be paid what their premier promised and Chris Minns promised huge pay increases in line with inflation," he told reporters.
"Now today, paramedics are walking off the job."
Two thousand HSU members, representing nearly half of all NSW Ambulance paramedics, have meanwhile threatened to allow their professional registration to lapse on December 31 if their demands are not met.
HSU members want a pay increase of about 20 per cent to put them on par with Queensland, one of several states draining NSW of skilled staff.
Hours of negotiations between the HSU and the government continued this week.
Health Minister Ryan Park has acknowledged paramedics' pay no longer matches the skills required.
But he has cited incoming budgetary pressures, including a need to give 1100 nurses full-time contracts, for not bowing to union demands.
Australian Associated Press