An online marketing consultant believes a politician's use of Snapchat to engage with teenage girls is a poor branding decision.

National's Chris Bishop says he downloaded the social media app last year and responded to people who messaged him on it.

READ MORE: Bishop did nothing wrong, but it was naive to talk to underage teens on social media, says expert

The Hutt South MP says he was trying to engage young people in politics.

But consultant Shannon Smith told Mike Hosking he questions whether that's the right audience to be targeting.

"In an election year people, who is my target market and who am I talking to, and certainly people under the age of 18 can't vote, so therefore why I am bothering talking to these people?"

LISTEN ABOVE AS SHANNON SMITH SPEAKS WITH MIKE HOKSING