"ACC does not know why dissatisfied people do not complain, and has not carried out any recent research to find out why" Ms Provost said.
However she noted that "if people see little value in complaining, then the number of complaints might fall because of people's confidence in the system and processes is weakened."
Ms Provost said significant issues revealed by her report that required attention were:
• relatively low levels of satisfaction from complainants on how ACC handles their complaints;
• limited organisational learning from complaints because of disconnected parts of the complaints system and disconnected recording of complaints; ? a lack of consistency throughout ACC's complaints system;
• a need to better equip staff with the skills, knowledge, and tools to handle complaints; and
• a need to do more to understand people's experiences of the complaints system and why some people do not complain.
Ms Provost made five recommendations to improve ACC's complaints handling process including seeking and implementing measures to make it easier for people to complain, maintaining a consistent record of complaints and the corporation's response, and better reporting of its performance in handling complaints.
ACC chief executive Scott Pickering, said ACC would implement all five recommendations.
Green Party ACC spokesman Kevin Hague said it was unacceptable that it had taken the Auditor General's before ACC took long-standing concerns about its complaints process seriously.
"ACC Minister Judith Collins came into the job over two years ago claiming she'd fix up the culture of disentitlement at ACC, but this report shows she has failed in that mission."
"The only real solution is to change the government and get ACC back to its core principles.
"Again, the Auditor General has shown that ACC views its role to be about cutting costs and its default position is to decline claimants and saving money."
The Office of the Auditor General (OAG) also released a report on the Ministry of Social Development's complaints process and found while it generally dealt with complaints professionally and had changed some of its practices as a result of complaints, it could take too long to deal with them and complainants were not kept well enough informed.
The OAG contracted a research agency to survey 669 people who had complained about Work and Income and StudyLink, and conducted fuller interviews with ten. They found while most believed their issue was resolved fairly in the end, only 36 per cent were happy with the way the complaint was handled. Many felt they had not been kept informed of progress and it took too long to resolve the issue. It also found some people believed their complaint would be acted on more quickly if they directed it to the Minister of Social Development (MSD) rather than their local Work and Income office. However, in reality that could slow the process down because it could take up to four weeks before replies were put before the minister to sign.
It said Work and Income was working with the Minister's office to try to ensure that if the ministers' office was contacted directly, they were told the formal complaints process was quicker.
The Auditor General found each section in MSD had its own processes which meant it managed complaints and reported on them inconsistently, although she said it was already looking at setting up a single process.
"A lack of consistency in the overall approach means that the Ministry cannot gain a complete picture of how many complaints it receives and resolves, and how well it responds to people who complain. This makes it more difficult to see where any systemic problems might lie.
Liz Jones, Acting Deputy Chief Executive of MSD said the department had acknowledged early on that it did not have a single complaints management system. "We are now developing a Ministry-wide approach to managing complaints across our various service lines. The aim is to have improved clarity around standards for managing complaints, response times and consistency of reporting."
She said she was pleased the OAG had acknowledged examples of good work in managing client complaints.