The pledge, which is to be made in an amendment to the Climate Change Act today, will make the UK the first country in the G7 to legislate for the target, which was based on advice from the Committee on Climate Change.
Prime minister Theresa May said that reaching “net zero” by 2050 was an ambitious target, but one that was vital to protecting the planet for future generations.
“Standing by is not an option,” she said. “Now is the time to go further and faster to safeguard the environment for our children.
“This country led the world in innovation during the Industrial Revolution, and now we must lead the world to a cleaner, greener form of growth.”
She stressed the need for other countries to follow the UK’s lead, saying a further assessment would be carried out within five years to confirm that other major economies were taking similar action in order to maximise the environmental impact and to prevent unfair competition.
Committee on Climate Change chair Lord Deben described the move as a major commitment that would send a strong signal to other countries to follow suit, but said it was just the first step.
“The target must now be reinforced by credible UK policies, across government, inspiring a strong response from business, industry and society as a whole,” he said.
The move was also welcomed by Environment Agency chair Emma Howard Boyd, who said it provided a powerful boost to efforts to tackle climate change.
“This is not only the right thing to tackle the climate emergency for future generations but a huge opportunity to increase our energy efficiency, improve our resilience and deliver a greener, healthier society,” she said.
But campaigners criticised the decision to continue to allow international carbon offsets, under which the UK could pay to offset its emissions elsewhere in the world.
“Fiddling the figures would put a huge dent in our ability to avoid catastrophic climate change – and the government’s credibility for taking this issue seriously,” said Friends of the Earth chief executive Craig Bennett.
“Having declared a climate emergency, parliament must act to close these loopholes.”
Luke Murphy, head of the environmental justice commission at the IPPR, said that although legislating for net zero made the UK a global leader in terms of climate ambition, far more substantial policy progress was required to deliver on that goal.
“On our current path, we’re not going to meet our current, less ambitious targets, let alone net zero,” he said.
“Filling that policy gap will require a transformational vision and programme of policies to deliver a sustainable, just and equitable economy.”
