The internet survey, involving more than 600 people throughout the country, was organised by Acclaim Otago, an ACC claimant support group.
ACC figures indicate long-term claimant numbers fell by more than 3600 or 25% to about 10,626 over the past three financial years.
About half the survey participants were former long-term claimants who had been removed from the scheme.
Critics say many clients were unfairly "exited" to save scheme costs, but ACC officials say the reduction reflects improved early intervention by ACC and better rehabilitation.
The survey examined what happened to former long-term claimants after they no longer received ACC support.
ACC emphasised the importance of rehabilitation and returning to work but the survey highlighted the "embarrassing" reality that, among participants, only about 25% of former claimants had gained any work, Acclaim Otago president Dr Denise Powell said.
In fact, only about 6% were working full-time, defined as 30 hours a week or more.
"There is a problem with exiting people from ACC without them first receiving meaningful rehabilitation."
Half of all former long-term claimants who were without work were now receiving Winz funding.
But most did not receive the unemployment benefit because a doctor had certified them either unable to work (invalid's benefit) or with limited ability to work (sickness benefit).
The other half could not receive Winz payments because their partner was working.
Of 92 survey participants who were found by ACC to be "vocationally independent" (fit to work full-time) about two-thirds had appealed the decision. And nearly half that group had regained entitlement.
A total of 123 people had been "exited" after having their file reviewed, but nearly half this group had also been reinstated.
New Zealanders should be "very concerned" about the figures because ACC were "obviously making decisions that don't reflect people's real injury status and clearly don't stand up to external scrutiny", given the high proportion of claimants reinstated, she said.
The survey, which had been running for the past two months, was not conducted along randomised, scientific lines, and participants volunteered to take part.
ACC senior media adviser Glenn Donovan said ACC did not report on the transition of long-term clients to paid work, but planned to do so in future and development work was under way.
ACC and Australian worker compensation schemes participated in the "Australia and New Zealand Return to Work Monitor", which surveyed samples of people who were injured at work and received 10 days or more of paid compensation.
For the 2011-12 year, ACC's overall "return to work" rate was 88% - 4% higher than the Australian national rate and another measure was 5% higher, he said.
