The tourism sector is officially New Zealand's biggest export earner, but it's putting a squeeze on infrastructure.

More than three and a half million tourists came here last year, one million more than six years ago.

AUT director of New Zealand Tourism Research Institute Simon Milne told Rachel Smalley it's hard to find accommodation in the main centres and it's putting pressure on the community.

"And if communities start to feel they're being put under pressure, that they're not really getting much in the way of direct benefit from the industry, but are bearing a lot of costs, then I think we're going to see an erosion of some of that goodwill from the hosts to the visitors."

LISTEN ABOVE AS SIMON MILNE SPEAKS WITH RACHEL SMALLEY