ACC Minister Judith Collins has gone into bat for the senior manager who was told of a potentially massive breach of client privacy in December but didn't do enough to investigate it.

ACC chief executive Ralph Stewart this week confirmed reports that in August last year a case manager accidentally emailed a spreadsheet with information about other clients to a long-term claimant.

About 9000 records were sent relating to about 6700 individuals giving information including their names and claim numbers.

He revealed that Philip Murch, ACC's national manager of Recover Independent Services, first learned of the potential breach during a routine meeting with the claimant in December but didn't inform his superiors.


"We didn't do enough at that point," said Mr Stewart.

Yesterday, following a meeting with Mr Stewart and ACC chairman John Judge, Ms Collins said she was expecting a report from the corporation and how it was handled as early as tomorrow.

Ms Collins said said Mr Murch "obviously didn't handle the matter as well as it should have been handled".

However she understood that during his December meeting with the recipient of the information, Mr Murch was not told "what the nature was of that confidential information" and was "not fully aware of what was happening".

"That's what I expect will no doubt be reflected in the report to me."

By yesterday about 2200 clients affected by the breach had been contacted.

Ms Shroff said it appeared the breach involved only ACC claims that were under review in August last year.