Prime minister says progress will be made at Cancún and austerity cuts should not dampen expectations

Britain's efforts to tackle climate change by pursuing a green economy must not be downgraded because of spending cuts and austerity, the prime minister says today.

Writing in the Observer on the eve of the Cancún climate talks, David Cameron says Britain is prepared to act unilaterally against climate change, "setting a shining example domestically for other countries to follow". He says ministers do not expect a global deal to be struck in Mexico, but he believes progress towards multilateral action will be made.

Cameron says the coalition's ambition is to be the greenest government ever formed. He argues for politicians to make the economic case for action and points out that the low-carbon market is worth up to £3.2 trillion and forecast to grow by 4% annually.

"I passionately believe that by recasting the argument for action on climate change away from the language of threats and punishments and into positive, profit-making terms, we can have a much wider impact," he says.