The man wrongly sent an email containing details of tens of thousands of Earthquake Commission claims says he is prepared to use the information in a dispute with the commission.
The EQC has complained to the police about Bryan Staples who it says had signed a statutory declaration to destroy the email.
Mr Staples runs Earthquake Services - a company that works for people dealing with insurance claims - and says he is owed $700,000. EQC says Mr Staples began the jobs the money relates to without prior approval but Mr Staples maintains he only did so after getting legal advice.
The EQC says Mr Staples advised it that if it paid certain accounts in full there would be no media announcement and the matter would go away.
Mr Staples told Radio New Zealand's Morning Report programme he told the commission that this matter - referring to the dispute over $700,000 - would die. "It does not mean that I'm going to shut up about what EQC are doing to the people of Christchurch."
Mr Staples said he had deleted the EQC email but his lawyer told him there was nothing to stop him retrieving it.
"(The statutory declaration) only bound me for what I had done up until that time that I signed it. It does not bind me today, tomorrow, next year, any time in the future."
A top privacy lawyer says if Mr Staples distributes the email, he could be taken to court by every one of those claimants.
Clive Elliott, an Auckland barrister, says if Mr Staples carries out his threat he will be harming a number of people's interests.
He says there would be both privacy and confidentiality breaches if the information was shared.
"EQC would be able to to take action against him, as would the people whose information he actually makes public, on the basis they may have sent him the information inadvertently but they notified him that he wasn't able to use it."
Mr Elliott says if it was used, harm would be caused.