Scientists have attacked Boris Johnson’s claim that an Oxfordshire facility is “on the verge” of creating commercially viable fusion reactors, saying the technology is decades away, and poses a distraction from the government’s failure to cut emissions.

In the prime minister’s Conservative party conference speech he referred to a fusion reactor called the Joint European Torus (JET) at Culham that he claimed would soon provide “virtually unlimited zero-carbon power”.

However, according to the organisation’s own website, commercialising this process will take another 30 to 40 years.

Mr Tony Roulstone, a lecturer in nuclear energy at the University of Cambridge told The Independent scientists are not claiming they have strong evidence it will even work – and certainly not in less than around ten years.

“Any claims to have the answer for commercially viable fusion reactors need to be treated with scepticism,” he said.

In a piece for The Conversation, Thomas Nicholas, a PhD candidate in fusion energy at the University of York, said it should not be used as an alternative to cutting emissions.

“The allure of fusion makes it a good distraction from the failures of the current government’s science and climate policy,” he said.

“The Committee on Climate Change has set 25 targets that need to be met to ensure the UK is a net-zero society by 2050. The government is currently only on track to meet one of them.”

JET is the world’s largest fusion reactor and earlier this year secured £92.1m in EU finding that will secure its future until 2020.

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Mr Johnson’s speech comes days after the announcement of new climate policies which include £330m for research into nuclear fusion to provide clean energy “by 2040”.

The concept of nuclear fusion involves squeezing together hydrogen atoms to make helium.

This releases vast amounts of energy, but currently it only works at extreme temperatures of more than 100,000,000C in order for the hydrogen nuclei to fuse. For it to be commercially viable, the process would need to produce more energy than it consumes, which is yet to happen.

If the technology is ready before 2050 it is already too late for the 1.5C target. The net-zero 2050 target assumes emissions decrease from now until 2050.

Greenpeace and Friends of the Earth have previously criticised the PM for wasting money on the “pipe dream” of nuclear fusion.

“Even if we could snap our fingers on December 31, 2049 and replace all fossil fuel plants, the world would have already emitted twice as much carbon as the budget allows,” said Mr Nicholas.

“Sound climate policy involves cutting emissions as soon as possible, and any further delay makes the task even harder.”

Craig Bennett, Friends of the Earth chief executive, said: “Why throw money away on tech-fix pipe dreams, at precisely the moment that onshore and offshore wind and solar are delivering better returns than ever before?