Text scandal: Judith Collins calls for National MP Andrew Falloon to leave Parliament today

National Party leader Judith Collins wants disgraced MP Andrew Falloon to resign from Parliament today, after it's believed he sent pornographic images to a 19-year-old woman.

UPDATE 7.50AM: Andrew Falloon has resigned from Parliament, effective immediately. The latest update can be found here. 

Yesterday Mr Falloon announced he wouldn't be standing at the election, saying he had made "a number of mistakes" and was dealing with "unresolved grief" after a friend's suicide.

It was later revealed Mr Falloon is alleged to have sent pornographic material to a 19-year-old woman.

Today Ms Collins says she wants him to resign from Parliament today, rather than leaving at the election.

"I've now come to the conclusion that with the shifting nature of his story, that it would be best if he resigned immediately from Parliament," she told TVNZ1's Breakfast this morning.

A source told 1 NEWS that Mr Falloon's explanations were not consistent and were continuing to change, raising further alarm bells among the party's leadership and senior staff. 

Ms Collins couldn't commit to whether she'd sack him herself, saying: "This is a matter for caucus but I am taking this very seriously."

Addressing recent claims Mr Falloon's phone was taken and another person sent the image, Ms Collins says he didn't tell her that.

"He admitted the allegation that the young woman had provided through to the Prime Minister," she says.

"The issue is that Andrew Falloon advised me he has significant mental health issues and that he's receiving help with that. 

"If someone tells me they have those sort of issues, then I take them at their word."

The young woman had contacted police initially before telling the Prime Minister's office, Ms Collins says.

Mr Falloon knew her in "a professional sense".

After the woman contacted the Prime Minister's office, they got in touch with Ms Collins on Friday. Ms Collins only spoke to Mr Falloon about it yesterday.

She defends the wait as necessary.

"It was important that I confronted him face-to-face with this issue" rather than over the phone or email, Ms Collins says.

Ms Collins says she's been in touch with the woman, telling her about her "disgust" at what had happened.

"My first concern was the actual health and the welfare of the young woman who has been the victim in this case," she says.

"Yesterday I emailed her and I gave her my personal cellphone number, as well as my email."

Ms Collins says she's heard reports that there are "likely to be other incidents" and encourages anyone impacted to contact her or the party's office directly.

'COME TO US'

Ms Collins says she wasn't aware of Mr Falloon's struggles with mental health issues and she wants other MPs to know they can come forward if they need help.

"That is what I would expect and my plea to any MPs is they should come to either the leader, or the whips, or someone else they can trust," she says.

"It's not acceptable to undertake this behaviour that he has done."

After confronting Mr Falloon in person yesterday, Ms Collins says the party booked him a flight home and had a colleague pick him up from the airport.

"I was not going to let Andrew Falloon, having told me that he has significant mental health issues, to just go home alone.'