Police are investigating self-styled justice campaigner Scott Guthrie, after another inquiry found he breached numerous regulations.
The Department of Corrections began an investigation after Checkpoint revealed Guthrie had charged an inmate's family thousands of dollars for support and advice dealing with the department.
Guthrie had been granted specified visitor status, allowing him access to inmates in jail, but it is against the law to take rewards or payments from prisoners in that role.
Guthrie also allegedly gave the impression he was working for charity.
A copy of an invoice from Guthrie, which a Northland family gave to Checkpoint, shows he charged them $10,000 for "support and advice," and "consulting with Corrections".
Initially he denied the invoice existed. But once Checkpoint's Lisa Owen explained the invoice had his correct name, address and contact details, and had come from his email address, he acknowledged the invoice was sent from him.
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Corrections formally revoked Guthrie's specified visitor status in September.
The department also referred the matter to police after its investigation reached conclusion.
Corrections found Guthrie knew that he should not have been receiving payments as a specified visitor.
"Our investigation found that Mr Guthrie received payment for providing services to prisoners, including through invoicing the whānau of a prisoner for providing services to the prisoner," Corrections' national commissioner Rachel Leota said in a statement.
"The investigation also confirmed that Mr Guthrie was aware he could not receive payment of any type from anybody for services delivered as a Specified Visitor.
"He had signed an application which specifically asked if he received any benefit or gift from or on behalf of prisoners, and he had ticked the ‘No’ response box."
Leota said Corrections' review found there are opportunities to improve the screening processes to approve someone as a specified visitor, and that work will be progressed.
Police have confirmed to Checkpoint they conducting further enquiries.