The National Party has confessed it broke the rules during the process of selecting candidates to replace outgoing MP Nikki Kaye.
But party president Peter Goodfellow, who was on the selection committee that didn't follow the rules, says he rejects any ideas the process was purposefully manipulated.
It comes after the resignation of Kaye, the MP currently holding the Auckland Central seat, when the party was forced to find a replacement candidate. She announced she was leaving on July 16 following former leader Todd Muller's surprise resignation earlier in the week.
Two candidates were shortlisted, Nuwanthie Samarakone and Emma Mellow. But according to the party's rules, the pre-selection committee must shortlist five candidates from which delegates will elect the nominee.
Goodfellow said in a statement to Newshub the committee had difficult decisions to make from a "wide pool of excellent candidates".
"In the case of Auckland Central nominations, the pre-selection committee, comprising a majority of local members, and chaired by the local electorate chair, voted unanimously to put forward two candidates to delegates," he said.
"In so doing it did not strictly follow the letter of our rules. The pre-selection committee has now acknowledged that and rectified the issue."
He adds the process to select a candidate wasn't manipulated, an idea he "absolutely and categorically" rejects.
"The National Party run extremely local and democratic selection processes, the most democratic of any Party in Parliament," he says.
"Auckland Central is the most marginal seat in the country and we are very focused on retaining it for National."
The party has since reopened the selection process and says it will have a candidate by August 10. It means National won't be able to stand its nominee at the first Auckland Central debate on August 9.
All candidates in the election have to register by August 21 with the Electoral Commission.
Other nominees contesting the Auckland Central seat are Helen White for Labour, and current MPs Chlöe Swarbrick from the Greens and Jenny Marcroft from New Zealand First. There are also candidates from the Outdoors Party, The Opportunities Party, ACT and an independent nominee.