The names of 479 Otago ACC claimants appear on a list of 6725 people mistakenly emailed to Auckland claimant Bronwyn Pullar late last year, in a major privacy breach.
The names of 137 people with "sensitive claims", involving rape and sexual abuse, were also included in the national list.
Several ongoing high-level inquiries, including by the Privacy Commissioner, were sparked by the email mistake.
The Otago Daily Times, through an Official Information Act inquiry to ACC on March 16, sought the number of Otago claimants involved.
Dr Denise Powell, the president of Acclaim Otago, an ACC claimant support organisation, said the figure obtained by the ODT this week showed the privacy issue clearly affected many Dunedin and Otago people as well as thousands of ACC claimants elsewhere in the country.
It is understood the 479 Otago people had initiated about 700 Otago-related reviews of previous ACC decisions in the 12 months ending on June 30 last year.
Dr Powell said the 479 figure revealed the remarkably large number of people in Otago who had been dissatisfied with previous ACC decision-making in a single financial year.
"It makes it very real," she added.
Under New Zealand's official information legislation, requests for such information must be answered within 20 working days, with a time extension allowed in some cases, but "you must be told of the extension and the reasons for it", the Ministry of Justice advises.
The ODT has also made a complaint to the Office of the Ombudsmen over the delays.
The delays were drawn to ACC's attention on May 24, but despite apologies and explanations about an oversight and administrative pressures, more than a further month went by before the information was provided.
In a letter to the ODT this week, ACC government services adviser Jon-Paul Bignold "sincerely apologises" and "sincerely regrets the undue delays" in handling the request.
"Unfortunately these delays were caused by administrative errors that resulted in your request remaining unanswered," Mr Bignold said.
Other ACC officials were approached yesterday to respond to criticism of the delays, and ACC trust issues, but no further comment was immediately available.
The emailed information sent to Ms Pullar involved a spreadsheet listing the names of ACC clients, relating to claims going through the Disputes Resolution Services Ltd review process between July 1, 2010, and June 30 last year.
The spreadsheet had earlier been sent internally to dozens of ACC managers throughout the country.
Dunedin lawyer Peter Sara said a "significant number" of Otago people had been affected by the privacy breach, and he believed ACC had later deliberately "done a go-slow " over the release of the information sought by the ODT.
A great deal of work, and not just offering some "bland phrases", would be needed if the public's trust in ACC was to be restored, Mr Sara said.
And ACC administrators should be more mindful about "accountability to the Fourth Estate", he said.
