Climate activist Greta Thunberg hit out at the Government as she joined demonstrators in London to protest over the planned development of the Rosebank oil and gas field.

The famous campaigner attended a demonstration outside the office of UK Energy Security Secretary Grant Shapps, as she urged ministers to be on the “right side of history”.

Mr Shapps is expected to decide soon on whether to approve the development of Rosebank, 80 miles north west of the Shetland Isles, which is believed to be the UK’s largest undeveloped oil and gas field and thought to be capable of producing up to 500 million barrels of oil.

Campaigners estimate that burning through that amount of oil would generate more CO2 emissions than 28 low-income countries produce in a year.

“The fact that the UK Government is even considering this tells us exactly how out of touch with reality they are,” Ms Thunberg told Channel 4 News.

“All the record-breaking heat waves and the extreme weather events we’ve seen during the summer is just the beginning of a rapidly escalating existential crisis.

“We will be seeing much more of this. This is not the new normal, it will continue to escalate and get worse until we start to take real action. And that’s why we need to do it now before it gets even worse.”

It comes amid concerns from climate campaigners that Rishi Sunak is considering watering down some of his government’s environmental policies in the wake of the Tory victory Uxbridge and South Ruislip by-election.

Success in Boris Johnson’s old constituency was pinned on local Conservative opposition to the expansion of London’s ultra-low emissions zone (Ulez), with some right-wing party members urging the Prime Minister to rethink the UK’s net zero commitments.

Mr Sunak has said he wants a “proportionate and pragmatic” approach to achieving net zero amid cost-of-living pressures.

Ms Thunberg warned that any such approach would be foolhardy.

She said: “To believe that you can focus on one crisis without also addressing the other is so very short sighted thinking. We seem to be physically incapable of having more than one thought in our head at the same time right now.

“And that’s very, very dangerous.”

She warned: “You have to be on the right side of history. We are many who are judging you and who are watching you.

“If you think that you can just get away with a few more years, a few more months of continued business as usual to maximise short-term profits, then you are very wrong and history will judge you very poorly.”