Prime Minister Bill English says Shane Jones will not be a threat to National MP Shane Reti in Whangarei.
"They'll vote for the guy who's got his feet on the street doing the hard work," English said.
"For a local MP, people vote on how hard the local MP works, how committed they are to the community.
Jones, a former Labour Cabinet minister who stood for the Labour leadership in 2013, is expected to be announced on Friday as New Zealand First's Whangarei candidate.
English said Reti was a very good local MP.