Hutt South MP Chris Bishop has been confronted about his social media messages to teenagers.

National MP Chris Bishop has defended his efforts to engage young people in politics and hit back at suggestions he was inappropriately messaging teen girls.

The MP for Hutt South put a statement on his Facebook page in response to anonymous complaints from some parents that he was messaging their teenage daughters through the social media app Snapchat.

Bishop said the story was "upsetting" as he explained the context of the social media interaction.

"In mid-2017 it was suggested to me that I open a Snapchat account, which I did. This proved very popular and lots of people sent me messages through it. I got into the spirit of things and would often reply to messages sent to me. Most messages were of support from people in Lower Hutt, including young people, for me/National," Bishop said.

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"However, after a few weeks I heard third hand that some parents were unsure about their kids communicating with MPs on social media. I adopted a policy of having a "Story Only" account and only having SnapChat friends that I knew personally," he said.

Bishop was allegedly confronted before last year's election by a mother upset at the older man messaging her daughter and other minors.

Witnesses said Bishop was taken aside and asked to stop what he was doing.

"I wanted to confront him as many parents felt very uncomfortable that their children were messaged," said a mother, who wanted to remain anonymous.

"He admitted it straight away and thanked me for bringing it to his attention."

Another mother, whose 13-year-old daughter was allegedly in daily contact with Bishop for a week or two on Snapchat, took to Facebook to vent her frustration.

The woman, who also wanted to remain anonymous, allegedly wrote to MP Paul Goldsmith to complain about Bishop's behaviour.

None of the parents were concerned that Bishop's intentions were anything other than misguided.

Bishop said his youth work in his electorate was a particular point of pride.

"As one of the younger MPs in the Parliament I see this as an important part of my job. I have enjoyed being involved in things like setting up the Hutt City Youth Awards and Student Leaders' events, and supporting the Young Enterprise Scheme, to name a few."

Throughout 2017, Bishop was invited to speak at a number of schools and other events about the importance of voting and our democracy.

Bishop initially refused to speak about the matter when approached for comment.

Experts said it was a salutary reminder of the perils of social media and the need for care. This scenario was not uncommon as a lot of people in positions of authority were warned about what is appropriate and not appropriate in terms of using social media to contact teenagers.

Social media consultant Jef Kay said that schools, for example, normally had their own platforms to contact students. His advice is that anyone wanting to contact students should use the school's platform rather than Facebook.

It would be "quite unwise" for a teacher to use Facebook or Snapchat to contact individual pupils as it could so easily spiral out of control.

Once a situation got out of control, it was very hard to recover from a mistake, and with Facebook, there was a permanent record.

The National Party's social media policy guide for 2017 advised against the use of Snapchat.

"At this time, it is recommended that MPs and candidates avoid using the Snapchat app as a public social media platform."

Bishop said it would be a shame if politicians were no longer able to work to engage young people in politics.

"Every election the media write stories about how young people don't vote, don't see any reason to vote, and how politicians are out of touch. I've set out to change that. It would be sad if politicians were put off engaging with young people because of stories like this."

Bishop was elected to Parliament in 2014 as a list MP and won the Hutt South electorate in 2017.