The State Services Commission has conceded it did a poor job monitoring the Ministry of Education's implementation of Novopay.
State Services Commissioner Iain Rennie says the commission should have provided ministers with better advice about the teachers' payroll system.
Novopay has been plagued with thousands of errors since its introduction in August 2012, with underpayments, overpayments or no payments at all to some teaching staff.
On Tuesday, senior Education Ministry official Anne Jackson resigned following a critical report into Novopay.
At Parliament's government administration select committee on Wednesday, Mr Rennie stuck to the line that officials were at fault, not government ministers.
State Services Minister Jonathan Coleman made it clear that the commission had failed in its role to properly supervise the implementation of Novopay.
Mr Rennie agreed. "We should have been providing ministers I think with not just snapshots of where the project was at, but more targeted advice to ministers about how they could appropriately intervene and shift that project forward.
"We didn't do that - I acknowlege that - and we have to do better in the future."
Mr Rennie said the commission lost its objectivity in monitoring Novopay.
Labour's state services spokesperson Phil Goff said he wanted to know why officials were being held responsible, rather than the ministers.
One resignation not enough - principals
Principals and teachers say it will take more than the resignation of a senior public servant to restore their trust in the Ministry of Education after the botched introduction of Novopay.
The inquiry found that officials misrepresented to government ministers Novopay's readiness to go live.
However, the primary teachers' union, the NZEI, said Education Minister Hekia Parata, her then- associate Craig Foss and Finance Minister Bill English did not ask the right questions.
NZEI national secretary Paul Goulter told Radio New Zealand's Morning Report programme their resignations are essential if teachers and parents are to trust the Government again.
The Te Tai Tokerau Principals Association, which represents Northland principals, said the politicians should demonstrate the same integrity Anne Jackson showed when she resigned.
Hekia Parata says she shoulders some of the blame for the botch-up, but maintains officials are to blame for misleading her, Mr English and Mr Foss.
Ms Parata said she and the other ministers were given either overly optimistic or inaccurate information which subsequently led to misinformed decision-making.
Ministry reviewing all IT projects
The Ministry of Education is reviewing all its IT projects to ensure it does not repeat the mistakes made with Novopay.
The ministry has multimillion-dollar projects underway, including a new system for tracking early childhood enrolments and a tool for helping teachers use the national standards in reading, writing and maths.
Acting Secretary for Education Peter Hughes says none of the projects come close to Novopay in terms of their scope, scale or cost. However, he says the ministry is reviewing them to ensure the lessons learned from Novopay are implemented.
Post Primary Teachers Association president Angela Roberts says the IT review is vital and will help prevent the ministry wasting money that would be better spent directly on education. Ms Roberts says the ministry needs to involve teachers and principals when it develops new systems.