Paramedics in the North and across the state will escalate industrial action next week after rejecting the government's latest pay offer.
It comes as records obtained under Right To Information show worsening ambulance response times, with the government rejecting criticisms it is choosing not to publish historic data to avoid negative press.
From Monday, paramedics will refuse to work overtime shifts across the North, North-West and South, while crews that are ramped at the conclusion of their shifts on Monday, April 20, will hand over their patient to an officer delegated by Ambulance Tasmania.
HACSU State Secretary Robbie Moore said members have continued turning up to work under enormous pressure.
"We've been in negotiations for 10 months. What more can ambulance staff and paramedics do? They've tried their best, they've tried to avoid taking industrial action, but if they don't bring this to a head, it'll never end and we will lose more and more paramedics," he said.
"It's disappointing that we have to take this action, and it will cause some inconvenience, that it's fully the government's doing by the way it has treated this workforce with contempt."
Minister for Health, Mental Health and Wellbeing Bridget Archer said the government remains at the negotiating table.
"We want to see Ambulance Tasmania staff get that pay rise as quickly as possible," she said.
"It's the nature of negotiations that they are, in fact, negotiated. We're still at the negotiating table, we're here, ready to have those conversations in good faith with HACSU on behalf of their members, and we really want to see that agreement finalised soon so that those hardworking members can get a pay rise."
Wait times 'significantly worsening'
In February, ambulance response times rose to 15.6 minutes, an RTI by the Tasmanian Greens shows.
Over the last two years, the average response time was 14.9 minutes.
The latest figures are a "significant worsening" of response times over the last two years, according to Greens' MP Cecily Rosol.
Ms Rosol accused the government of hiding the monthly response times to keep the public knowing what is really happening with the ambulance service.
"The government should be transparent, and make it easily available so all Tasmanians know what's happening in our ambulance service," she said.
Before February, the Health System Dashboard showed monthly ambulance response times across the state.
Now, the site only shows daily response times.
Ms Archer rejected a suggestion the State Government was attempting to bury the data to avoid bad coverage.
"I think it's ridiculous to suggest that we are trying to bury data that we have, in fact, made more transparent," she said.
"When we came to government, there was no reporting around these numbers at all. And we have progressively introduced greater levels of transparency, including now moving to daily reporting of ambulance response times."
Ms Rosol said the government should be honest with Tasmanians.
"The government can say they're being transparent, and they can say they're not hiding things, but that doesn't match the practices that they have," she said.