Call waiting times to reach Housing New Zealand's 0800 contact centres are likely to blow out again next month as it turns on the computer systems underpinning its $92 million transformation programme, the crown corporation has warned.

Citizens Advice Bureau policy adviser Andrew Hubbard said the organisation had been briefed.

"We do have some concerns about whether services are going to be as available as they should be. We just have to cross our fingers and hope for the best."

The CAB said in May that it was not uncommon for tenants and its own staff to have to wait 20 minutes to reach Housing NZ on the phone after it began channelling all inquiries through its call centres and requiring tenants set up an appointment to meet tenancy managers.

Housing NZ transformation manager Philippa Jones said it had got on top of those issues, which were caused by inquiries from people checking their eligibility for state housing "going through the roof" and calls were answered in less than three minutes on average every day last week.

However, spokesman David Balham said it was "highly likely" waiting times would increase again from August 10, when Housing NZ switches on new software supplied by Britain's Northgate and United States firm Oracle which is designed to better automate many of its processes.

Jones forecast the "bedding-in period" could last up to about six weeks as staff got used to the new systems.

"We do expect we will be slower on things initially. You can train your staff as much as you like but learning in the 'classroom' accounts for about 10 to 20 per cent of your learning and the rest is done on the job."

Jones said Housing NZ had contracted in 20 extra people to handle calls, would have another 100 on hand to help manage the transition and had provided a dedicated email address and some online "self-help" tools for voluntary groups such as the CAB that provided advocacy for tenants.

It was confident it would be able to handle "all emergency situations".

Many tenants called between 9am and 11am on Monday and it would help if they could not call then regarding any less urgent matters, she said.

Jones said 9000 separate tests had been carried out on the software systems and Housing NZ was confident all critical systems worked to its satisfaction.

"If you were to test every single thing in the system you would be here for a couple of years."

Labour housing spokeswoman Annette King said Housing NZ had not been clear enough in its communications with tenants about what to expect come August 10 and the transformation project, the cost of which had blown out from $72m, had not gone as planned.

"That is why they have had to take on 70 staff over and above what they were going to," she said. 

- © Fairfax NZ News