Key Points:

State Services commissioner Mark Prebble says Ministry for the Environment chief executive Hugh Logan told him two months ago that David Benson-Pope had expressed a view about having Madeleine Setchell in his ministerial office, but he forgot about it.

Dr Prebble overlooked the information when he wrote a piece for the Dominion Post two weeks ago stating that Mr Benson-Pope was not involved in the decision.

Mr Logan has since reminded him of it and he has recalled hearing it - though Mr Logan did not alert him to the discrepancy when he saw a draft of Dr Prebble's statement to the paper.

Following David Benson-Pope's resignation from Cabinet last week, Prime Minister Helen Clark criticised Mr Logan for not disclosing the conversation between himself and the minister to Dr Prebble's deputy, Iain Rennie, who handled the matter in his absence overseas.

Mr Rennie also made misleading statements because of Mr Logan's failure to disclose the conversation to him.

Dr Prebble defended Mr Logan, however, saying "he had not been consciously withholding stuff. It's just the speed with which things have come out in the past couple of weeks has been highly confused".

Ms Setchell lost her job as communication manager for the ministry after Mr Benson-Pope told Mr Logan he would be less free and frank when she was in his office because her partner worked for National leader John Key.

When that became publicly known last week, Mr Benson-Pope lost his job because it contradicted denials he gave in interviews that he had made his view known.

Dr Prebble defended the right of ministers to express views about who came into their offices.

"A minister is entitled to have a view about who is in their office. It is actually not uncommon. Work in and around the heart of policy sometimes gets quite tense."

He said it was unusual but not extraordinary for a minister to say he didn't want someone. "And that is something we manage. Life is like that. It isn't in itself necessarily job-threatening. In fact it oughtn't to be."

Dr Prebble has decided to investigate the matter himself, to decide whether it was correctly handled from a public sector point of view and what lessons to draw from it.

National State Services spokesman Gerry Brownlee has criticised the inquiry saying it is a matter of the SSC investigating itself because Dr Prebble advised Mr Logan before he made the decision.

Dr Prebble said the matter was at the heart of setting the standard for state service interaction. "It is my job. I don't think getting someone independent to do it would actually get me off the hook. I'm still responsible for enunciating standards in this area."

Dr Prebble acknowledged that different views about what constituted conflict of interest had emerged but he thought that was healthy.

"I know what's behind it is that people are proud of having an apolitical public service and so am I."

He would not be assessing the conduct of any politician, however, because that was the function of Parliament.

He said he wanted to look at the factors that led to Ms Setchell's employment, whether a conflict of interest was reasonably identified, and whether it was addressed "with appropriate political neutrality".