Porirua City Council chief executive Wendy Walker says she did the right thing.

A council boss says she did the right thing after revelations her council spent almost $76,000 checking six "unusual" car refills by a former mayor.

Porirua City Council chief executive Wendy Walker called police a week before 2019 elections, making initial contact about mayor Mike Tana's petrol card spending. She then informed councillors by confidential email - which leaked to media, triggering most of the costs.

Ultimately the queries about six refills of the mayoral Holden Captiva went nowhere, but cost $20,987 for an external review, and $54,806 in legal bills.

The cost, covering petrol spending totalling below $1000, was slammed by now ex-mayor Tana as inappropriate and "just mad".

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Walker, however, stood by her decisions, saying the costs could have been avoided if only Tana answered sooner. "I think I did the right thing at the right time."

Andrew Turner Former Porirua mayor Mike Tana says the council should have believed him and saved itself 75-odd thousand dollars.

She said most of the costs came after the leaked email about police contact to councillors, which included Tana's main mayoral rivals.

This was about three weeks after she first asked for an explanation from Tana about the refills made unusually close together. There was no detailed explanation forthcoming from the mayor.

"I gave him a lot of rope to work with, and ... he was really just not answering at all."

Walker said it was her judgement call on the timing of her contact with police, and informing the councillors.

"I don't think that potential anomalies in spend should be held back because there's an election."

Joel Maxwell Incoming Porirua Mayor Anita Baker receives the mayoral chains from Porirua City Council chief executive Wendy Walker at the swearing-in ceremony for the 2019 term held at Pataka in Porirua.

Walker said she faced public abuse for simply following the correct process. "It actually turned into a thing about me, not about Mike Tana, I think. That's my perspective."

Tana said if the chief executive had "just listened to me in the first place" then the council could have avoided the costs.

He said he told her he never used the card inappropriately - and pointed out they had never put in a process for recording his use, such as a logbook, that would allow him to show that.

"Because of that - and I guess they didn't believe me - they've wasted $75,000 of ratepayers' money. That's just mad."

Spending the money was "wholly inappropriate, especially when I told her that I had never done anything wrong", he said.

KEVIN STENT/STUFF Porirua mayor Anita Baker says she backs her chief executive.

Tana said the bigger ramification was the decision had a "significant" outcome on the elections, which he lost to new mayor Anita Baker by 397 votes.

Walker denied the leaked inquiry into the ex-mayor's card spending had any impact on the outcome of the elections.

"The way I read it is that actually Mike's supporters galvanised and got more people out in his favour. It's six of one and half a dozen of the other."

An Ernst and Young report in the final week of the election found about 64 per cent of travel on the days in question was for personal use: Tana made a couple of trips to Palmerston North to pick up one of his children, and drove another to his Wellington school.

The report didn't draw any conclusions from the findings, instead leaving Walker to evaluate the "reasonableness" of the petrol spending.

Private use of the mayoral car was allowed under his agreement.

Walker said she did not pursue the case further with police because Tana had "provided the information that I had been asking for".

"I'm not a judge in any of these things, I'm the chief executive for the council ... so it's up to the council to decide on the outcome."

In December, councillors voted unanimously that no further action would be taken over the issue.

Mayor Anita Baker said Walker was holding the council responsible for the ratepayers.

"I back what Wendy has done, I don't like the cost of what happened, but this could have easily gone away if Mike had answered in the beginning."

She "absolutely" did not regret the extension of Walker's contract for another two years from August, decided since the elections.