Labour has ceded the west Auckland electorate of Waitakere to National.
Social Development Minister Paula Bennett will keep the seat that she won by nine votes on a recount, after special votes had put Labour's Carmel Sepuloni ahead by 11 votes.
Labour secretary Chris Flatt told Fairfax Media the party decided not to challenge the result after considering how much time and money it would cost.
A petition could have cost $30,000 to $50,000 and possibly more than $100,000 if Labour had chosen to challenge on the basis of malpractice.
NZN