"These seconded staff were located throughout New Zealand, near to the approximately 250 clients with long-term sensitive claims they were looking after."
The case managers are in 12 regional offices and had been dealing with sensitive claims since last November.
Ms Cosgrove said all the seconded staff underwent intensive training in sensitive claims management, including training around preserving client privacy.
"In addition, access protocols were agreed for claims and no paper files were transferred," she said.
Ms Cosgrove said care was taken to ensure clients were properly advised of the change.
But ACC claimant advocates Denise Powell, of Acclaim Otago, and Auckland-based Kyle MacDonald, said they only became aware of the move after one claimant learned by accident her new case manager was based in a branch office.
"That was quite upsetting for her."
Ms Powell understood affected claimants were advised they had new case managers, "but ACC didn't necessarily state that their case manager was no longer based in Wellington".
"My understanding was the SCU was set up to be a stand-alone unit and was specifically isolated from the mainstream of ACC in order to ensure the utmost protection of those people's information and identity," she said.
Mr MacDonald, who is a member of the Sensitive Claims Advisory Group, which ACC regularly meets with, said the corporation never raised the change with his organisation. "The reality is 250 claimants are now being managed outside of the Sensitive Claims Unit in regional branches by case managers who are not sensitive claims specialists."