Prime Minister Bill English has dismissed New Zealand First leader Winston Peters' call for him to resign over the Todd Barclay controversy.
Mr Barclay has announced he will resign by not standing for National in this year's general election.
Police have reopened an investigation into whether the Clutha-Southland MP secretly recorded staff in his electorate office.
Mr English told Morning Report that Mr Peters was "just saying things" to get into the media over the "issue of the week".
"Which I think tells you that his strategies - like running on the fact that the regions are falling behind - just aren't working, so he's trying to find others."
But he said the party would need to work hard to beat Shane Jones, who was confirmed last week after months of speculation as New Zealand First's candidate in Whangarei.
Watch the PM's interview with Guyon Espiner in Auckland:
"We've got a hard-working MP there [Shane Reti] and we'll need to work hard to win."
Three years ago, Mr Jones - a former Labour MP - left politics, crossing the party divide to become the government's Ambassador for Pacific Economic Development.
Mr Peters won the neighbouring seat of Northland, which was previously a safe seat for National, in a by-election in March 2015.