Carbon emissions markets could deliver a “substantial part” of the £60 billion a year needed by 2020 to help poor countries tackle climate change, Gordon Brown has said.

A report for the Prime Minister said global carbon trading could reduce the cost of cutting emissions by up to 70 per cent, enabling much deeper cuts and making it more likely to keep temperatures from rising to a level which would cause “dangerous” climate change. In schemes such as the EU emissions trading scheme, overall limits are set on greenhouse gases and companies or countries are required to purchase “allowances” to cover their output.

They can either reduce their emissions or buy allowances from others who have cut theirs, which ensures the cuts in greenhouse gases are made where it is cheapest to do so. The report, by the Prime Minister’s special representative on Carbon Trading, Mark Lazarowicz, said carbon markets should be combined with regulation, taxes and public money for comprehensive action.

Industrialised countries should have ambitious national targets to cut emissions and a network of cap and trade systems, such as the EU ETS. Emissions trading schemes put a price on carbon and ensure that the emitter pays for their pollution, the report said. Cap and trade schemes could provide finances for measures such as paying poorer countries to refrain from deforestation and support their transition to low-carbon economies.

Mr Brown said: “The carbon market can deliver a substantial part of the 100 billion US dollars a year needed by 2020 to help developing countries reduce their emissions, tackle deforestation and adapt to climate change.” But Keith Allott, head of climate change at WWF-UK said: “Crucially, the rich world must also help developing countries to curb the growth in their emissions at the same time.”

And he said: “There needs to be a huge reality check.

“Today’s report shows that the rich world is currently proposing to cut emissions by just 7-9 per cent by 2020, less than a quarter of what is needed.”