People fighting for ACC payouts have said they faced "intimidation, misinformation and an orchestrated campaign of harassment".
In a self-selection survey, 600 people were questioned on their experiences with ACC.
Their responses form part of a report which urges the United Nations to recommend changes to what it describes as an "unfair procedure" for people with disabilities who dispute ACC findings.
Bruce van Essel said has been on and off ACC since 1995. He said he has been accused of fraud four times, raided by police and had so many reviews, he's 'lost count'.
"It just seems to be continual and neverending. Treatment that I have received from ACC over the years has been shocking, and degrading."
He said he's paid out more in legal and medical fees than he's received and has been made to feel like a second class citizen.
"It's bad enough having to deal with an injury, and getting on with your life as best as you can, but then having them on top of you all the time - it just makes life a lot worse."
Mr van Essel is the president of the ACC support group, Acclaim Otago, and is one of more than 600 people whose experiences have been used to produce a report for the United Nations.
Acclaim Otago said ACC is breaching the UN Convention on the Rights of Persons with Disabilities, particularly those challenging ACC decisions to stop their payments. It said people face systemic problems including ACC reviewers relying on hearsay or their colleagues' opinions, and reinterpreting expert conclusions.
The report's main author, barrister Warren Forster, said the main issue is the financial constraints stopping people paying for lawyers or expensive medical tests.
"Legal aid is not effective and it's not available. The costs awarded are a fraction of what it costs a person. Because of the financial position that the person is in, they have no ability to carry that cost, so most of them are unable to obtain (legal) representation, and that is a massive problem."
The report makes three recommendations including introducing an independent commissioner, and reviewing costs and rates for legal aid. It also recommends suspending plans to have cases heard by a tribunal rather than a district court.
In a statement, ACC said the Government had responded to a previous report by the UN Committee on the Rights of Persons with Disabilities.
A spokesperson for ACC Minister Judith Collins said it's not common practice for ministers to comment on individual submissions to the UN.