Climate campaigners have threatened the UK Government with legal action over approving a huge controversial North Sea oil field development.

Activists have warned Tory ministers and the North Sea Transition Authority (NSTA) over legal action over the impending decision on whether or not to approve the Rosebank oil field off the coast of Shetland.

It is believed that UK Energy Secretary Grant Shapps is set to shortly give Rosebank the green light after months of protests and political opposition to the field.

The UK Government has been open about its intention to expand the exploration of new North Sea oil and gas developments, using energy security as justification to allow more fossil fuels to be burned.

The campaign group Uplift has written to Mr Shapps and the NSTA stating that it has strong grounds to believe that approval of Rosebank would be unlawful.

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It claims a potential failure to ensure a transparent and participatory decision-making process, the incompatibility of Rosebank’s development with the UK’s climate targets, a potential failure to assess the environmental impacts created by burning Rosebank’s oil and the marine environmental impacts of the field make approving the scheme unlawful.

The challenge from Uplift comes in the wake of fresh warnings from climate scientists that the world is on track to break the 1.5°C global warming threshold within the next four years .

On Wednesday, the UK Government’s statutory advisers, the Climate Change Committee, stated that expansion of fossil fuel production is not in line with net zero ambitions.

The advisers warned the UK Government has “sent confusing signals on its climate priorities to the global community”.

In a new report, the CCC added: “Support for new oil and gas, beyond the immediate increase in gas production demanded by the Ukraine invasion, and the decision to consent a new coal mine in Cumbria have raised global attention and undermined the careful language negotiated by the UK COP26 Presidency in the Glasgow Climate Pact.”

The Rosebank development would see a pipeline laid through a protected area of the North Sea, the Faroe-Shetland Sponge Belt, with warnings it could potentially harm the eco-system and the diverse marine life it supports.

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This includes delicate coral gardens and rare, deep sea sponges; to clams and numerous species of whales and dolphins.

Tessa Khan, climate lawyer and executive director of Uplift, said: “We have repeatedly raised concerns about the calamitous environmental impacts of Rosebank but this government seems determined to bury its head in the sand.

“Aside from the abundant evidence that new oil and gas projects are incompatible with a safe climate, the approach that the government is taking to a decision on Rosebank gives us strong grounds to believe that an approval of the project would be unlawful.”

She added: “Our planet can no longer sustain new oil and gas and our broken energy system in the UK certainly can’t.

"Given that our addiction to fossil fuels is at the root of the energy crisis facing this country, this government should be 100% focused on ways to lower UK energy bills.

“Instead, through tax breaks, they are effectively pouring money into the coffers of oil companies Ithaca Energy and Equinor, which is majority-owned by the Norwegian state.”

Scottish Greens environment spokesperson, Mark Ruskell, said: “If the UK Government is serious about their climate commitments, then it must end all new oil and gas exploration.

“With the world burning around us and the UK failing to hit its targets, it is clear that Rosebank cannot go ahead. It's hard to think of anything that could be more reckless or destructive. “

He added: "This week's Climate Change Committee report underlined how desperate the situation is. The crisis is getting worse but Downing Street is going backwards.

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“Whilst Downing Street continues their profit-hungry drive to extract another 500 million barrels of oil from the North Sea we are already seeing the devastating impacts of the climate crisis right on our doorsteps.

“In the last few weeks alone we have seen soaring temperatures, forest fires and record heats around the world. We really have no time to waste.”

The UK Government said that new oil and gas licences simply reduce the fall in the UK supply and will not increase it on current levels.

An NSTA spokesperson said: "The NSTA does not comment on individual cases.

“We remain fully committed to reducing emissions across the industry as a whole and our production projections, even with new developments, show a continuing decline to 2050 in alignment with the global 1.5C reduction target.

“We are also working hard to take significant action in areas such as carbon capture, only recently announcing offers of 21 storage licences.

“We are holding North Sea industry to account on its commitment to halve emissions from production operations by 2030. Strong progress is being made, with overall emissions down by more than a fifth between 2018 and 2021 and flaring cut in half over the last four years.”