National leader Simon Bridges says he retains confidence in Invercargill MP Sarah Dowie and she won't be stood down, despite a police investigation into a message sent from her phone to Jami-Lee Ross.
But he said he does not condone her behaviour, in relation to the text in question.
Police are investigating a text message, allegedly sent from Dowie's phone to her former colleague and Ross.
The police investigation is said to focus on whether the text message - which came after the break-up of their extra-marital relationship - constituted an incitement to self-harm, which is punishable by up to three years in prison.
Ross, 33, has previously named Invercargill MP Dowie, 43, as one of the women with whom he had an extra-marital relationship while National MP for Botany.
The text message included the words: "You deserve to die."
Bridges said today he still had confidence in Dowie, who has been an MP since 2014.
"She's been an effective, hard-working MP," Bridges told MediaWorks.
"Look, it'll be tough right now, but I think if she can get out demonstrate that again... she can be again an effective MP."
Bridges stopped short of condoning what Dowie allegedly said in the text, but said it had to be viewed in context.
"Everyone that I've been talking to can see what this is - and that's a personal relationship that's gone badly wrong."
Dowie would not be stood down during the police inquiry, Bridges said.
Speaking to RNZ this morning, Bridges said he did not condone the text allegedly sent from Dowie's phone to Ross.
He would not say what conversations he had had with Dowie, in relation to the incident, but said she had not offered to stand down.
"Ultimately I do have confidence in her – she is a hardworking, effective MP."
He said people have private lives and it was not his job to get involved in that.
Asked if he still backed her, he said he did.
He would not be drawn on the context in which the text was sent, other than to reiterate that it was "a personal relationship that has ended very badly".
"I'm sure, as is the case of all these things, there are two sides to this story."
Ross initially received the text message in August but has claimed reading it two months later led to considering self-harm. He was taken into mental health care shortly after.
The text message raised questions over whether there was a breach of the Harmful Digital Communications Act, passed under National and voted for by Dowie. The law regulated digital communications, including text messages, making it illegal to urge someone to self-harm.
The fact of the police investigation was revealed by Ross during a television interview. It was apparently sparked by a call to the Crimestoppers hotline. Ross said he did not lay the complaint.
Ross and Dowie were understood to have been in a relationship for more than two years. It is believed to have ended around May.
During that time, Dowie and Ross were both in marriages with children each. Dowie and her husband later separated.
The text message which is the focus of police inquiries was made public last year in the wake of Ross' explosive departure from Parliament.
It followed claims of inappropriate behaviour towards female colleagues, leading to Ross disclosing two extramarital relationships.