Some of Australia's peak conservation groups fear the country's natural heritage will be lost because state and territory governments are declaring their national parks "open for business".

Commercial enterprise and development in national parks is set to happen in parks for the first time in generations, with several jurisdictions recently amending conservation laws to allow businesses to operate.

The Northern Territory is the latest jurisdiction to open its protected parks to new business, after Queensland and Victoria recently made similar amendments.

Queensland has already approved one new tourism venture in a national park and is considering many more.

"One permit has been issued and negotiations continue with another proponent," said a spokesperson for the state's National Parks Minister Steve Dickson.

Forestry canopy tour project One of the first projects being considered for national parks is a zip line tour at Kondalilla National Park in Queensland's Sunshine Coast hinterland. Zip lines, which are becoming popular in tourist destinations around the world, stretch between trees and allow people to slide on a course of wires through a forest canopy. The Sunshine Coast tour would take people through the remnant forest above the Obi Obi Gorge near Montville. The company developing the tour already runs one zip line operation, at Hollybank in Tasmania, and is also developing another at Toolangi north of Melbourne. It uses platforms called cloud stations, which are clamped onto large trees for people to stand on. The company says the specifications of its proposal are still being determined and that the forest will not be harmed by the installation process.

Four other proposals have been deemed fit to proceed by the Queensland Government but are yet to engage in the permit process, while a further 11 proposals have been referred to government departments for further progress.

The Queensland Government changed the state's Nature Conservation Act last year to allow new business ventures in its parks.

The first tourism venture to take advantage of the move is a solar-powered boat cruise up Lawn Hill Gorge in Boodjamulla National Park in the Gulf country.

A Tasmanian-based zip line operator is also developing a proposal to build a zip line in the Kondalilla National Park on the Sunshine Coast hinterland.

Like Queensland did, the NT Government is now calling for expressions of interest.

In a statement, it said it is opening up 86 parks and reserves "to unlock the full visitor potential in these areas while contributing to the conservation of the Territory's natural environment".

Victoria announced it would make the same move in 2012, amending legislation to allow 99-year leases over parts of parks.

This has allowed development proposals to be put forward for some of the state's most significant natural areas, like the Grampians.

Most recently, the Victorian Government announced it will allow development within the Point Nepean National Park on a former quarantine station.

Conservationists say move 'driven by ideology'

But conservationists have questioned the need for such development, saying it would erode the protection of natural heritage that national parks are supposed to provide.

"National parks are held in trust for the people of Australia. They're not owned by any state government or any business, so their primary function is to act as a park for the protection of nature," said Australian Conservation Foundation campaign director Paul Sinclair.

"Fundamentally I think a lot of it is just driven by ideology.

"I think there's a sense from some people, who just don't get it, that they resent the idea that there are some parts of our country that are protected for wildlife."

The Queensland Government does not have economic modelling for what it hopes to gain from increasing commercial activity in the parks, but said it based the policy on recommendations from a steering group and the tourism industry and an unpublished evaluation of the previous government's nature-based tourism initiative.

It said the success of ecotourism businesses in Tasmania was an inspiration for its policy decision.

"The Queensland Government has set an ambitious target to grow tourism, and especially visitor expenditure, in the state to $30 billion by 2020," said the spokesperson for Mr Dickson.

"Ecotourism, through Queensland's huge diversity of landscapes and marine life, is a key competitive tourism advantage that has the potential to become an important driver to help achieve this target."

The Queensland National Parks Association has opposed the move since it was first proposed.

Executive director Paul Donatiu said the change threatened the key purpose of national parks, which is to protect landscapes from human interference.

"Elevation of commercial use of national parks to one of the key objects of the Nature Conservation Act directly threatens the very natural values that national parks seek to conserve," he said.