Prime Minister Boris Johnson will this week commit Britain to cutting carbon emissions by 78 per cent by 2035, almost 15 years earlier than planned, in one of the most ambitious environmental targets set out by a developed nation.

The new timetable, which will require a fundamental restructuring of the way British homes, cars and factories are powered, comes after China and the United States agreed that stronger pledges were required to tackle climate change.

Britain’s opposition parties and environmental campaigners welcomed the ambition but said the move had so far been undermined by the government’s lack of policies to deliver it.

Greenpeace said the building of new roads and runways would have to stop. “Targets are much easier to set than they are to meet, so the hard work begins now,” it said.

Mr Johnson will make the commitment, to cut emissions by 78 per cent from their 1990 levels, this week ahead of a US climate summit that will be hosted by President Joe Biden and before Britain hosts the UN Climate Change Conference, known as COP26, in November, a person familiar with the situation said.

Britain set a greenhouse gas emission target in 2019 of net zero by 2050, in line with the 2015 Paris climate agreement which called on countries to take steps to keep the global temperature rise as close to 1.5 degrees Celsius as possible.

Tom Burke, a former government adviser, said the UK’s approach to cutting emissions had so far looked like a “Boris blunderbuss” with a huge range of marginal moves rather than a co-ordinated structural change.

“The most important thing I think is to focus his policy around energy efficiency, around wind and solar and around storage of electricity and the management of the grid,” he told BBC Radio.

Myles Allen, head of the Climate Dynamics Group at the University of Oxford, said the government would also have to work out how, and who would pay, to dispose of carbon dioxide safely.

“Disposing of carbon dioxide safely by reinjecting it back under the North Sea always costs money because it is far, far cheaper to fly tip it into the atmosphere,” he said.

The Financial Times said emissions from international aviation and shipping were likely to be included in the target, a decision that was welcomed by environmental groups.

-Reuters/AAP