The Law Society has used a rare legal gag order to attempt to conceal a new case of alleged sexual harassment or bullying by a senior lawyer.

The super-injunction – the first such hard-line suppression known of in New Zealand – was granted by High Court Justice Peter Churchman after the Law Society bungled a complaint file and inadvertently sent details to another person who had nothing to do with the case.

Super-injunctions became notorious in the UK and some other overseas jurisdictions because not only do they stop embarrassing information being disclosed – but they also mean the very existence of the case must be kept secret.

This New Zealand order, made on March 29, came to light after the email's mistaken recipient challenged the super-injunction as an unacceptable threat to open justice.

READ MORE:

* 'A lot of anger' around Law Society report

* Lawyers' sexual harassment 'worst kept secret' for decades

* Widespread harassment, bullying, racism in law

* Outspoken #metoo lawyer barred from Law Society panel on misconduct

Stuff learned of the matter and joined the proceedings, applying for the High Court to both lift the super-injunction and, further, to be allowed to reveal that this was a new case of alleged sexual harassment in the legal profession. The confidential nature of the contents of the email and the persons involved was not challenged.

The bungling of another case of sexual harassment is embarrassing for the Law Society, coming so soon after the the outcry over its handling of sexual harassment at law firm Russell McVeagh and at university law schools.

Late on Thursday, High Court Justice Rebecca Ellis issued new orders effectively allowing Stuff to disclose the fact of the proceeding, the super-injunction, and the botched sexual harassment or bullying case that it was designed to conceal.

On Thursday evening, Law Society president Kathryn Beck sent an email apologising to lawyers for the "completely unacceptable" privacy breach.

"The breach occurred through the incorrect application of an 'auto fill' email function," she said. "The email concerned a complaint to the Law Society and it was incorrectly sent to one individual with a similar first name.

"Upon realising the error, the Law Society immediately contacted the unintended recipient and requested the email be deleted, but no response was forthcoming. All parties involved were informed as soon as possible. The Office of the Privacy Commissioner was contacted and our approach followed that office's guidance and its Privacy Breach Guidelines.

"The Law Society has directly apologised to the individuals concerned for this unacceptable mistake. The Law Society also took the entirely appropriate step of seeking a Court order to prevent any publication of the email in order to protect the privacy and confidentiality of the information and people affected."

The Law Society has been under pressure in recent months for its handling of sexual harassment issues in the wake of the Russell McVeagh revelations, in which four summer interns claimed serious sexual misconduct on the part of senior lawyers.

A subsequent survey of all registered lawyers found a third of all female lawyers and 14 per cent of all male lawyers said they had been sexually harassed at work. Kathryn Beck said she was "surprised and caught out" by the results.

But after that, a number of lawyers have stepped forward to tell Stuff of disclosures made to the Law Society.

Wellington Women Lawyers' Association convener Steph Dyhrberg said it seemed inappropriate that the Law Society couldn't confirm investigations in cases where there was a public interest.

"Everybody knows about the Russell McVeagh issue, knows about the alleged conduct and the Law Society can't even say 'yes, we are looking at it'," she said.

"That causes a lot of speculation and anxiety."

Although this is believed to be the first time a super-injunction has been used here in New Zealand, they have been controversial internationally. Due to their nature of secrecy, it's not possible to say how many have been issued, nor how many still exist.

The most famous of the super injunctions was applied in the case of English footballer Ryan Giggs, who tried to keep secret details of his extramarital "threesome" with a Big Brother contestant. The injunction failed to hold when Giggs' name began trending on Twitter, and the MP John Hemming outed Giggs as the holder of the super-injunction, under Parliamentary privilege.

Former Top Gear star Jeremy Clarkson's super-injunction stayed in place for a year to prevent his ex-wife publishing details of their personal life. In 2011 he applied to the British High Court to have it lifted, saying: "Injunctions don't work, they're completely pointless and unbelievably expensive."

Amid concern about a lack of transparency, the UK set up an official committee on super-injunctions in 2010. It found they could become a danger to the principles of open justice, and should be used only in the very short term.