Bronwyn Pullar wrote to Cabinet Minister Nick Smith 18 months ago accusing him of covering up corruption at ACC and warning him he would need public relations help in the face of anger over its policies.
In an emotional letter, she said ACC was "rotten to the core" and said she had numerous examples of claimants' rights being trampled on that would "seriously embarrass you".
The letter was sent in October 2010 as part of Ms Pullar's battle to get funding for treatment for her injuries.
She also sent it to the The New Zealand Herald which was investigating the high number of injury claims turned down by ACC on the basis of a pre-existing degenerative condition.
"This is NOT a mistake as you are making out Nick," Ms Pullar wrote.
"You are just covering up corruption that is alive and well within ACC.
"ACC is rotten to the core and I have numerous examples that could seriously embarrass you, over and above this."
She wrote that the "abusive processes" had to stop.
"Good luck fighting it Nick in the media.
"You are going to need big PR help on this one. It is everywhere!"
The letter emerged yesterday as Labour continued to demand an independent inquiry into the scandal that brought down Dr Smith.
A senior minister in John Key's Government, Dr Smith resigned his portfolios this week after it was revealed he had interfered in ACC's handling of his long-time friend and National Party activist Ms Pullar's claim while he was ACC Minister last year.
Ms Pullar yesterday issued an apology to Dr Smith.
"It is truly regrettable. I know you were only trying to help a mate - I wish you well Nick," she said in a statement.
Ms Pullar also detailed her own privacy grievance against the corporation yesterday.
She said an ACC staff member had improperly accessed her claim file seven times and lied to management about it.
That matter was the subject of an investigation.
Ms Pullar also said ACC had earlier this week leaked her name to the media.
"[ACC] set out to intentionally destroy my privacy and reputation - an excellent example of how little regard ACC has for claimants' rights including respect for their privacy.
"It shows how ACC treats claimants with disdain.
"It shows how ACC will smash anybody who dares speak out. Yet I am not easily intimidated," she said.
Mr Key yesterday resisted calls for an independent inquiry.
"Everyone has moved on. There is nothing I have seen in the paperwork I have that gives me concern about the need for an investigation," he said.
