The state health insurer would cut funding to physiotherapists by a third from November 16, saying it was "unaffordable for levy payers".
The new funding deal also allowed physiotherapists to charge for their services, while changing how, and how much, they were funded.
New Zealand Society of Physiotherapists president Jonathan Warren expected practitioners would charge between $10 and $20 per visit.
"We think the profession will suffer quite a bit, with people not accessing physiotherapy like they should," he told NZPA.
Two years ago, an independent review found physiotherapy services were underfunded by 33 percent, Mr Warren said.
"The physio profession is already being squeezed at the moment. The decrease in subsidy is such individual businesses will have to charge between $10 and $20 [per session].
"It's going to be a shock for some people -- particularly at this time, during the recession."
Though they could now charge a part payment, he was unsure whether physiotherapists could make back the cost of the service they provided.
"Around the world, New Zealand physiotherapists are internationally recognised as being highly trained and highly competent.
"It's easy to pick up work overseas. Unfortunately, if the money dries up, and it's not able to be recouped, physios will go."
This could indirectly contradict the Government's promise to not cut front-line health workers, he said.
The move followed a March announcement from ACC Minister Nick Smith, who said the organisation would cut entitlements in response to a blow-out in treatment costs.
The care was budgeted to cost $9 million when introduced in 2004, but was now costing $139 million and was projected to rise to $225 million by 2011-12 with no equivalent rise in rehabilitation rates.
ACC spokeswoman Gail Kettle said the insurer was cutting the amount paid to physiotherapists by a third, and a disproportionate number of those using the service were from higher socio-economic groups.
"We are also concerned that free physiotherapy has not led to more rapid recovery for clients who are injured. We are very clear that where we fund physiotherapy, we want to see measurable client benefits," she said.
