UPDATED 3.28pm The idea of imposing a conservation levy on tourists is gaining traction, with United Future now proposing the idea as part of an environmental policy package.

Both National and the Greens have already mooted variations of such a move.

United Future leader Peter Dunne said a $25 levy would be imposed on tourist visas, with the cash raised used to maintain and upgrade the conservation estate.

Mr Dunne said the cost of maintaining walking tracks, rivers and lakes currently fell on locals.

He disputes any suggestion the levy would be a turn-off for tourists.

"It's a very small price to pay, and I'd be very surprised if anyone decided not to come here on the basis of a $25 tourist visa to enhance the local environment."

Dunne also wants to see grants provided to boost solar power uptake and the use of electric cars.

He said $15 million would be spent annually on the proposal.

Dunne said the funding is not a lot, but it's a start, and the focus is on getting people to consider the technologies.

"We've been deliberately quite modest in the costing of some of these initiatives, because we recognise that you start small and you build up, but I think that would be a significant shift forward."

The new policy comes after the Green Party last month announced a "Taonga Levy" to fund conservation efforts and regional tourism, and that would increase current border charges for international visitors by between $14 to $18 to a total border levy of around $40.

Major tourism organisations, including Air New Zealand and the Tourism Industry Association, are currently working on proposals for a large central fund for tourism infrastructure.

Prime Minister John Key has said funding ideas, including a tourist tax or levy, would be considered.

Other policies in United Future's environmental policy package include:

• A $5 million annual grant to promote electric vehicle ownership, that would allow up to $5000 to be claimed, or up to 30 per cent of the cost of a vehicle, whichever is smaller. The scheme would also apply to businesses replacing company fleets. • A $10 million per annum contestable fund for promoting innovation and research into the environment.

• A fund of the same value for homeowners to purchase solar panels and similar units, with homeowners able to claim up to $5000 or 80 per cent of the cost, whichever is smaller.

• Develop new protection categories for marine reserves that would ban commercial fishing and allow recreational fishing.

• Get government to take a lead in encouraging owners of unproductive farming land to gift it to public ownership so it can be planted with native trees and act as a permanent "carbon sink".