The Auditor-General has referred allegations that parliamentary staff of MP National Maggie Barry were asked to carry out party political work during work hours back to the Parliamentary Service.

Auditor-General John Ryan has written to the Parliamentary Service to say that a specific investigation by the service should be carried out and he intended to inquire no further into the matter at this stage.

"The concerns were raised in the context of a broader investigation into an employment matter, and have therefore so far been considered only in that context. My understanding is that a specific investigation into whether there has been a breach of the appropriation has not yet been carried out.

"We therefore consider that further investigation into the concerns is necessary. After discussions with staff from your office, we have decided that the most appropriate course of action is for the Parliamentary Service to carry out that investigation," Ryan said in the letter to Parliamentary Service general manager Rafael Gonzalez-Montero.

Ryan said he would reconsider looking further into the claims depending on the outcome of that investigation.

The Auditor-General was brought in after a former staffer who accused Barry of bullying, including the allegations she expected staff to do political work on taxpayer time, laid a complaint with the office about misuse of public money.

Barry has denied both the bullying allegations and any concerns about a misuse of public funds.

She admitted her parliamentary staff had done National Party work but it was in their own time and using their own email addresses.

The Weekend Herald revealed in November that the Parliamentary Service had investigated claims from two former staff in Barry's office last year that Barry swore at and belittled staff.

Barry said a workplace investigation had cleared her of bullying charges.

National leader Simon Bridges has stood by his MP, saying he was not concerned about the Auditor-General's involvement.