Gareth Morgan's The Opportunities Party would ban subsidies on fossil fuels, increase the price of carbon and overhaul energy efficiency efforts under a climate change policy launched this evening.

The party argues that New Zealand needs a plan to get to zero-carbon economy by the middle of the century, at a time when the country still emits around 7.5 tonnes of carbon dioxide per person - much higher than the world average of 4.9 tonnes.

"Climate change isn't going away, and New Zealand needs to have net zero carbon emissions by 2050," said the party's chief of staff, Geoff Simmons.

"Currently we don't even have a plan.

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"TOP's plan is to have a proper price on carbon, one that reflects the challenge of meeting our 2030 and 2050 targets."

Its policy, announced in Dunedin, would cancel a surplus of carbon credits the Government intended to use toward future climate commitments, then develop a plan to reduce emissions over time, using an approach similar to the UK's Climate Change Act.

The Emissions Trading Scheme (ETS) would be overhauled by setting a carbon budget, removing the current upper limit on the carbon price and keeping the scheme closed to international credits.

The party expected this would raise the price of carbon, generating revenue that could be used to help households and businesses become more energy efficient, and provide a new incentive to plant one million hectares of erosion-prone land.

The party would keep agricultural methane emissions out of the ETS in the short-term, but nitrous oxide emissions from agriculture - mainly from nitrogen leaching and fertiliser use - would be brought into the scheme.

Also in the policy were moves to scrap subsidies on fossil fuels; phase out carbon subsidies to energy intensive exporters; require all landlords to insulate up to a modern code; and change the mandate of the Electricity Authority to include meeting New Zealand's existing target of 90 per cent renewable electricity by 2025 and 100 per cent renewables by 2035.

Simmons said the party chose Dunedin to launch the policy as many of the 9000 houses at risk from sea level rise within our lifetime were located in the city.

"This is a red zone waiting to happen, and we can't just leave vulnerable people to face this alone.

"The response requires some long term thinking from the community, local authorities and central government."

Under the Paris Agreement, the Government has pledged to slash its greenhouse gas emissions by 30 per cent from 2005 levels and 11 per cent from 1990 levels by 2030 - a target that would be achieved mainly through carbon trading mechanisms.

The Government is also enacting changes to carbon trading, including phasing out the one-for-two ETS subsidy, which allowed some businesses to pay one emissions unit for every two tonnes of pollution they emit.

The initial 50 per cent unit cost increased to 67 per cent from January 1, and would rise to 83 per cent from January 1, 2018.

All sectors in the ETS would pay the full market price from January 1, 2019.

Alongside the ETS review, the Government has established three expert groups to plant more trees, reduce agricultural emissions, and adapt to the environmental impact of climate change, as well as invest $2 billion in public transport, $20 million annually in agricultural greenhouse gas research and $200m for international climate-related support.