The Human Rights Commission has received five complaints in the past two years about Accident Compensation Corporation files sent to prospective employers.
The commission on Wednesday said in at least one case, the file included sensitive claim information such as sexual abuse.
ACC's policy of forcing clients to sign a wide-ranging privacy waiver has been found in breach of the law.
The Dunedin District Court ruled on Monday that the controversial ACC 167 form was beyond the law and the corporation had no right to decline entitlements because a client would not sign it. The corporation had cut compensation to an unknown number of claimants for refusing to sign the waiver.
Christchurch Justice of the Peace and community board member Karolin Potter said she had been approached by two people at legal forums who told her they had had sensitive claim information sent to their employer by ACC.
"In response to employer's request for their ACC information, the ACC had sent out the entire file including sensitive claim material for sexual abuse in their past."
Ms Potter told Radio New Zealand's Nine to Noon programme on Wednesday both complainants said ACC told them it had no discretion to filter the information they provided to prospective employers.
ACC has issued a statement saying it does not send information about claims older than 10 years, mental injuries, declined claims, treatment injury claims or sensitive issue claims, without the client's express permission.
The corporation said it will disclose information only if it is required to help get a client into work, which is the purpose for which it was collected.
Council of Trade Unions' president Helen Kelly says people signing employment privacy waivers are in no position to negotiate its conditions.
Listen to full interviews on Nine to Noon
Govt questioned over ACC policy
Opposition parties are questioning how long the ACC Minister has known about a privacy waiver used by the corporation that has now been ruled by a court as too broad.
Judith Collins. Photo: RNZ
ACC Minister Judith Collins, questioned in Parliament, said she was told about the court decision on Friday and was not aware of the significance of the issue.
But Labour and the Greens say Ms Collins has known about the issue for years, as it was raised in a report about a privacy breach 18 months ago.
Green MP Kevin Hague said after serious privacy breaches by ACC in the past, Ms Collins made public confidence in the corporation a ministerial concern.
Labour's ACC spokesperson Iain Lees-Galloway said it was implausible Ms Collins heard of the issue only last week.
"It was in the review of the Bronwyn Pullar case that issues with this form were first identified. In fact, there were media articles about this late last year as well. It's implausible the minister only heard of this issue last week."
In August 2011, details of more than 6000 ACC clients were mistakenly sent to Auckland claimant Bronwyn Pullar, resulting in the resignations of ACC minister Nick Smith, ACC chair John Judge, two directors and chief executive Ralph Stewart.
Outside the House on Wednesday, Judith Collins said ACC should not be handing over people's sensitive claim information to prospective employers and she hadn't heard about the sensitive claims complaint until Wednesday.
"I am actually very concerned about that and I want to find out what are the facts behind it. Is this correct? I understand that there has been some complaints filed with the Human Rights Commission. If that is true, I look forward to seeing what has occurred and when it has occurred."
Ms Collins says she wants to make sure that people's privacy is protected.
ACC checks for claimants penalised
The woman whose complaint about a consent form prompted the Dunedin court ruling said it should not take ACC long to work out how many people it has unfairly cut off.
ACC admits it may owe "considerable sums" for cutting entitlements to claimants who refused to sign the waiver and said establishing how many people had payments cut unlawfully will be a long process because it involves a large volume of data.
But Denise Powell said she and others received a letter with the code NCO-03 that stopped their payments and ACC should have no trouble tracing those documents.
Dr Powell told Radio New Zealand's Morning Report programme complaints about the ACC 167 have been raised since 2010. She said it was "in and of itself used as a "non-compliance tool" as part of efforts to reduce the cost of long-term claimants.
The day after the court ruling ACC reinstated one person it had cut off twice, and is looking back over 14 years for others it penalised.
Listen to Denise Powell
Private insurer believes its forms are lawful
A private insurer that manages claims on behalf of ACC says it doesn't believe its own privacy form is unlawful.
Privacy waiver forms used by at least one third-party insurer, Work Aon, are nearly identical to the unlawful ACC form.
Work Aon didn't return Radio New Zealand's calls on Wednesday, but another private insurer, Well NZ, says it believes its own forms are lawful.
Marketing manager Cliff McCord says Well NZ uses a more limited consent form.
"If you injured your back, for example, we would go to your physiotherapist and your GP and ask for a copy of your medical notes, what their investigation was, what the treatment was, what they think the diagnosis is. We could go to ACC and look at a history of back injuries, if you had multiple problems. But that's the extent of it."
Mr McCord says Well NZ won't be reviewing its form.