PHILIP Hammond has been accused of “creating obstacles” to tackling climate change after a leaked letter from the Chancellor to Theresa May warned that the UK Government’s target to cut carbon emissions would cost taxpayers well over £1 trillion.

The Prime Minister is coming under increasing pressure from scientists, experts, health professionals and environmental groups to set a legal target to reduce the UK's emissions to "net zero" by 2050 before she steps down in mid-July.

The calls have come in the wake of a report from the Government's advisory Committee on Climate Change[CCC], which recommended putting the new goal into law to cut greenhouse gas emissions by 100 per cent by 2050.

The committee said the target, which was needed to tackle climate change, could be achieved at the same cost as the existing legal target to cut climate pollution by 80 per cent by mid-century and would deliver economic opportunities.

Under a net-zero target, emissions would have to be largely eliminated from electricity generation, transport and heating, with a switch to renewables, electric vehicles and an end to traditional gas-fired boilers for heating homes.

Any remaining pollution by 2050 from areas such as agriculture and flying will need to be offset through measures to capture carbon such as planting trees, hence the reference to “net zero”.

In his letter to Mrs May - leaked to the Financial Times – Mr Hammond refers to how the CCC has estimated that reaching net zero will cost £50 billion a year but the Department for Business, Energy and Industrial strategy estimates the figure at £70bn.

“On the basis of these estimates, the total cost of transitioning to a zero-carbon economy is likely to be well in excess of a trillion pounds,” he declares.

This, the Chancellor claims, will have profound implications for households, businesses and the Treasury.

He warns it would require increased Government spending and reducing money available for other areas such as schools, hospitals and the police.

While Mr Hammond says he backs setting a net-zero target as soon as possible, he notes how the UK is off track on meeting interim "carbon budgets" to cut emissions and a new target will require ambitious policies in this parliament.

The Chancellor suggests a review should be undertaken before a new legal target is set.

But John McDonnell, his Labour shadow, said: “We are facing a climate emergency and Philip Hammond clearly doesn't get it.

"The Tory Party is way overdue in adopting a target already put forward by Labour, and now the Chancellor is creating obstacles to prevent the action we desperately need to take," he added.

Sir Ed Davey for the Liberal Democrats said Mr Hammond had got his sums wrong and the cost of tackling the “climate emergency” was massively outweighed by the long term cost of inaction.

“He might be trying to reclaim his crown as a fiscal hawk in the dying embers of May’s premiership but this intervention is wrong-headed and threatens our children’s future,” declared the former Energy and Climate Change Secretary.

“The time to act is now. Just this week a new report concluded that 30,000 premature deaths could be avoided by stopping the burning of fossil fuels, proving a clean future is a healthier future.

“With ambitious, stable, policies, Britain can have a competitive green economy, benefitting from the lower cost of hi-tech renewable energy,” added the London MP.

Doug Parr, chief scientist for Greenpeace UK, accused the Treasury of "putting their ideology before our well-being" and failing to include the benefits of a switch to a net zero economy.

"If you want to know whether a policy is a good idea, you include the benefits as well as the costs, and in this case the benefits include an economy fit for the 21st century, cleaner air, warmer homes and maximising the chances of civilisation surviving.

"The Treasury need to put the necessity of a green future above their nostalgia for a time when environmental threats could be dismissed as a niche issue.

"If reality doesn't fit with their models, it's the models that need to change," he added.

The Treasury said it would not comment on leaks but it is understood the Chancellor is not blocking a move to net-zero emissions.

The PM’s spokesman also declined to comment on a leak but said: "We committed to legislating for net zero back in 2016, we commissioned the report by the CCC to help shape our progress. We have not published Government analysis of the costs.”

He went on: "The CCC's advice last month indicated that achieving net zero would fall within our existing spending plans."

Asked whether Mrs May wanted the target as part of her legacy before leaving office next month, the spokesman replied: "The Government has a record to be proud of in terms of the action it has taken in tackling climate change."

He added that the Government would respond to the CCC report "as soon as we can".