Auckland former dentist Cam Calder will be sworn in on Tuesday as a National MP, but uncertainty remains over why the man he is replacing resigned from Parliament.
Richard Worth resigned as a National MP on Friday afternoon, just over a week after he stepped down as Internal Affairs Minister, and a day after Prime Minister John Key said he had "washed his hands" of him.
Dr Worth says he is quitting in the interests of the National Party.
Police are investigating a criminal complaint of a sexual nature made against Dr Worth. He has been separately accused of sexual harassment of a woman who is a Labour Party member.
Dr Worth says he has not committed any crime, but cannot defend himself against hearsay and scuttlebutt. He says Labour's fingerprints are all over a campaign against him.
But Labour Party leader Phil Goff is rejects the accusation, saying Dr Worth resigned because of the complaint made to police.
Dr Calder says he never wished to get into Parliament as a result of someone else's misfortune and regrets the circumstances. However, he says he is looking foward to the challenge.
He says he has spoken to Dr Worth, who wished him well.
Dr Calder was briefly in Parliament after the 2008 election before National lost a seat on special votes.
Radio New Zealand's political editor says no one has yet said exactly why Dr Worth has resigned and Mr Key is sure to be questioned further this week about the matter.
On Friday Mr Key said Dr Worth's resignation was a sensible course of action, which will give the country an opportunity to focus on issues that matter.