However, these pledges are not expected to be enshrined in a legally-binding international treaty in Paris because many countries, including the United States, would never agree to such a deal. Britain is instead pushing for strict new legally-binding rules governing how national emissions are monitored and reported - arguing that enforced transparency and scrutiny will provide political pressure on countries to meet their plans. Amber Rudd, Britain's energy and climate change secretary, said: "It's clear we need to take urgent action to tackle global warming and move to a low carbon future to ensure our long-term economic security. "That's why I want a global deal in Paris which will create a level playing field for businesses and drive innovation." However, she warned that "securing an ambitious deal will require a global effort and there is much work still to do". The pledges that have been made ahead of Paris still leave the world on track for warming of at least 2.7 degrees above pre-industrial levels this century – well above the 2 degrees level that scientists say should not be breached if the world is to avoid the most dangerous effects of climate change, such as extreme heatwaves and flooding.

This year is already expected to be the hottest on record and to breach 1 degree global warming for the first time, the World Meteorological Organisation last week confirmed. Britain and others are therefore also pushing for strict five-yearly reviews at which countries will be obliged to set out deeper emissions cuts in future, as the costs of green technologies come down. Nick Mabey, chief executive of environmental think tank E3G, said that most countries supported a five-year review mechanism, but "India and Saudi Arabia are trying to water down the rules in order to keep using fossil fuels". He said it was "critical" that a strong monitoring system, such as that proposed by Britain, was set up in Paris to check counties kept their promises. "If people think others are cheating then they won't support faster emission reductions at home," he said.

But transparency rules could also face opposition, with China traditionally "reluctant to allow international monitoring, as it guards its sovereignty closely", he said, although this was no longer a "hard red line for them". Britain already has its own legally-binding targets for cutting its greenhouse gas emissions through the Climate Change Act, which requires an 80 per cent cut on 1990 levels by 2050. Although many countries want to see all pledges made legally-binding, Britain is understood to be sympathetic to the US view that a "hybrid" approach, with voluntary targets but compulsory scrutiny, may actually lead to a more ambitious deal. The US never ratified the 1997 Kyoto Protocol, which imposed legally-binding targets on industrialised nations, while countries such as Canada faced no sanctions for withdrawing from the protocol and failing to hit the targets. Speaking last week, Todd Stern, the US special envoy for climate change, said: "We are quite convinced that there are many countries who would be inclined to put in a lower target than they're really capable of if they were worried about the legally-binding nature of the targets themselves."

Negotiators hope a voluntary approach will avoid a repeat of the 2009 Copenhagen summit, when talks on a binding deal ended in acrimony. One of the biggest hurdles to a deal in Paris is likely to be money. Poorer nations want industrialised nations to commit billions of dollars to help them fund the costs of going green. The Telegraph, London