She said the incident appeared to be a case of human error and poor judgement, and would be addressed with staff and appropriate action taken.
All WINZ offices contain locked, secure disposal bins for the destruction of personal information but procedure was not followed in this case.
Social Development Minister Paula Bennett said it sounded like a case of human error.
"You always hope something like this won't happen so it's disappointing when it does."
The clients involved in the latest leak were being contacted, and the Privacy Commissioner's office was being notified.
The Privacy Commissioner's office confirmed it received notification of the breach.
Wairarapa Advocate Service co-ordinator Trevor Mackiewicz said he thought the recent security breaches were unacceptable.
"It's a concerning thing if something happened because we want to know how it happened and why. It can be distressing on the clients who get the information and those clients who had their information given."
Mr Mackiewicz said he did not think this kind of privacy breach was a common occurrence, but had managed one case in which a client alleged a case manager was giving confidential information to the client's partner.
He has recently noted concerns from clients about the layout of the office as well, which some felt was not private enough and they worried others were hearing personal information.
The Masterton-based advocacy service has worked with about 65 Work and Income clients since it set up in January this year, and fields queries from up to 65 people a month.
The latest privacy blunder follows the Ministry of Social Development closing self-service kiosks at WINZ offices across New Zealand after blogger Keith Ng revealed he was able to access thousands of private files on ministry servers.
An independent inquiry will look at how the breach occurred and what can be done to prevent another one.
