The mayor of Invercargill says he has forked out more than $500 for a rental car to travel to a conference after a request to cover the cost was stymied by his deputy.

Sir Tim Shadbolt paid $523 on the hire car to travel to Palmerston North from Wellington for the annual Local Government New Zealand conference which is underway today.

The distance between the two cities is 190km.

Shadbolt said it was likely the Invercargill council "would have received a cheaper corporate rate" had they had agreed to the cost of renting a car.

In comparison an Uber to the venue from Wellington Airport would have cost around $260.

Shadbolt said the cost of his rental car would now be taken to the council for a decision on reimbursement next Tuesday.

"If this is not a complete misuse of council time, I don't know what is," said an angry Shadbolt.

"This highlights the need for reform.

"There should be rights that come with the Office of Mayor that can not be politicised or withdrawn - the first being the right to budget and staff," he said.

Shadbolt earlier said he was likely to take a taxi between the two cities after deputy mayor Nobby Clark, who initially approved the expenditure, changed his mind in an email sent on Saturday.

He labelled the move "petty and small-minded" and accused Clark, who is running for the mayoralty, of having a conflict of interest.

The Invercargill Ratepayers' Association did not want to comment.