Parliamentary Service boss says his staff didn't leak Nick Smith investigation details

The head of the Parliamentary Service has given assurances his staff didn't leak details of an investigation into outgoing National MP Nick Smith to journalists.

Dr Smith abruptly announced his retirement on Monday afternoon, citing personal and professional reasons including that details of an employment dispute had been leaked to the media.

These details are yet to emerge, despite Dr Smith saying he had been advised they would be made public on Tuesday.

On Wednesday morning, Parliamentary Service chief executive Rafael Gonzalez-Montero assured a Select Committee his staff did not leak any information.

Gonzalez-Montero said he had "confidence" in his staff but refused to say how he knew they were not responsible for the leak or comment on the employment investigation.

National leader Judith Collins has neither confirmed nor denied reports she was the one who warned Dr Smith about an upcoming media report.

A Politik article claimed she told Smith last Friday the story would be published this Tuesday in relation to his incident, and also claimed she warned her caucus early last month that media were about to break a scandal involving one of the party's MPs.

Collins told Morning Report it would not be fair to not let MPs know of any adverse stories in relation to them beforehand, but did not specify what if anything she had in fact told her caucus or Smith anything.

"Whenever I hear of any stories that may be adverse to any of our MPs, I will always let them know. And I'll let them know because I will not allow MPs to go stumbling into a situation where they have no warning."

She said any discussions with her caucus were confidential.

"I'm not someone who is going to advise media or leak things to media from caucus and I think it's very important that I don't."