WWF-UK welcomed the decision, saying it represented a significant and meaningful step towards a low-carbon UK, although scrutiny of the detail will be vital.

But WWF also said the struggle the self-proclaimed “greenest Government ever” had to endure in order to agree it does leave concerns over how committed some Government departments are to tackling climate change.

“No other country has set legally binding emission reduction targets going into the 2020s and so with this decision the UK is demonstrating genuine leadership on climate change,” said Keith Allott, WWF-UK’s head of climate change. “The Climate Change Act remains a groundbreaking piece of legislation that with support, will underpin the UK’s transition to a low-carbon economy.”

“However, we must remember that the Committee on Climate Change had made clear that the carbon budget agreed today is the “absolute minimum” necessary, and that it should be achieved through actions taken here in the UK rather than relying on emission credits from overseas.

“The unwillingness of Government to accept this recommendation suggests that some Whitehall departments are more committed to action than others.”

WWF is keen to see more countries follow the initiatiive of enshrining emissions reductions targets into law.  The UK’s Climate Change Act, passed in 2008, provides a framework for UK emissions to be reduced to at least 80 percent under 1990 levels by 2050 – a target consistent with the reductions advocated by the the Intergovernmental Panel on Climate Change.