Manukau Mayor Len Brown says using his council credit card for personal spending was a mistake and he won't do it again.
Mr Brown, who is standing for the Auckland super-city mayoralty, has been criticised by two councillors.
He says that there were three instances where he shouldn't have used the card and that he paid the money back promptly.
Once, he says, he forgot to take any money to a store; another transaction was reimbursed because he was unsure what it pertained to; and a third expense was incurred by his office, not him.
The council's chief executive, Leigh Auton, says council rules were not contravened, but two councillors, Jami-Lee Ross and Dick Quax, say business and personal expenditure should remain separate.
Mr Brown says he won't use the card for personal spending again during the rest of his term.