A war of words has erupted between National and the Greens, all over the idea to make our tourists pay for some of our conservation work.

Conservation Minister Maggie Barry has rubbished the Green Party proposal to charge an extra $14 when tourists enter New Zealand, saying it's a half-baked attempt to take credit for a successful pest control programme.

Green Party co-leader Metiria Turei said the programme is actually dangerously underfunded.

"The Minister has no role in protecting New Zealand's conservation because she is so fundamentally flawed. She is just one of the most useless ministers we've had in a long time, frankly."

However, Forest & Bird have applauded the Green Party's launch of the Taonga Levy yesterday, saying it shows that major political parties are taking the idea of a predator free New Zealand seriously.

Advocacy Manager for Forest & Bird Kevin Hackwell said the announcement by came as a surprise, especially after the Government officially adopted the policy of making New Zealand predator free two weeks ago.

"It's really good to have major political parties supporting the proposal that New Zealand goes predator free by 2050, and to have them actually, in the sense, competing with each other about how well it should be resourced to make it happen."

The levy almost doubles the tax foreign tourists pay but Ms Turei said most tourists won't even notice the change.

Mr Hackwell said they are very impressed with the possible $46 million a year that could be invested.

"It's clearly a significant investment which will make a big difference in achieving to have us goal and to doing the research and the work that needs to go on to make it happen."

However, the Tourism Industry Association says the levy could discourage tourists from coming here and could hurt our largest export sector.

Chief executive Chris Roberts said tourists already contribute a huge amount to the tax take.

"Our overseas visitors are already more than paying their way. They're contributing over a billion dollars a year in GST."

Mr Roberts said it would discourage people from coming here, which could actually reduce how much we raise from tourists.

"It would deter some of our visitors from coming and it sends a signal that we only see our visitors as a problem, not as our greatest earner of export earnings."