Gordon Brown today said a new global treaty on climate change had been "held to ransom" by some countries opposed to a deal in Copenhagen, and called for reform of the way such negotiations take place, including an international body to handle environmental stewardship.

The prime minister said the weak agreement reached in Copenhagen at the weekend after all-night deliberations was a "first step towards a new alliance to overcome the enormous challenges of climate change". He called on all countries to show greater ambition as part of a campaign over the coming months to turn the agreement into a legally binding treaty.