A legal challenge is underway in Edinburgh over the decision to grant consent to Britain’s largest undeveloped oil field.

A judicial review brought jointly by environmental groups Greenpeace and Uplift is being heard in the Court of Session.

The activists want to stop the development of the Rosebank oil field, which is off Shetland, and the Jackdaw gas field, off Aberdeen. But oil companies say the projects are vital.

If the challenge is successful, operators would have to resubmit environmental impact assessments for approval before drilling can begin.

Activists calling for the projects to be stopped staged a protest in front of the court on Tuesday morning.

Consent to drill in the Rosebank field was granted by the regulator, the North Sea Transition Authority (NSTA), last September.

Shell’s proposals to develop the Jackdaw field were approved by the NSTA in 2022 after initially being rejected on environmental grounds.

Environmental groups say that when consent was granted for the fields, the impact of emissions from burning the extracted oil and gas was “illegally ignored” by regulators.

Uplift accused regulators of “not being transparent” in granting the deals and said Rosebank would harm marine life in the North Sea.

The UK government said in August it would not fight any case for Rosebank and Jackdaw.

He effectively accepted that the original decisions were illegal.

This came after the Supreme Court ruled in June that regulators must consider the full environmental impact of new projects – including how fossil fuels are used by end consumers.

It is understood the oil companies will accept that the decisions to give the go-ahead for Rosebank and Jackdaw were illegal because the emissions they would create were not properly assessed.

They are expected to focus instead on how to move forward with the projects given that work is already underway.

Philip Evans, from Greenpeace UK, said: “Earlier this year the Supreme Court made it very clear that the climate impact of emissions from burning fossil fuels must be assessed before any new oil and gas projects can be approved .

“These types of emissions are what’s causing the climate chaos we’re seeing around the world.

“But the oil companies want to keep drilling for maximum profits while ignoring the damage they are doing.

“That’s why we’re suing Shell, Equinor and Ithaca to stop them in their tracks.”

Tessa Khan, chief executive of Uplift, said Rosebank should never have been approved.

She said: “Rosebank is a terrible deal for Britain. It is mostly oil for export, which would do nothing to reduce fuel costs or increase our energy security yet, because of huge tax breaks for new drilling, the British public would effectively cover almost all of the costs of developing it over time which oil companies leave with profits.

“It will not provide long-term security for oil and gas workers either.

“Even with new fields being approved, industry-supported jobs have more than halved over the past decade. Workers need clean energy jobs that have a long-term future.”

Lord Deben, former chairman of the government’s watchdog the Committee on Climate Change, said: “Rosebank and Jackdaw should never have been approved by the previous government.

“These fields will do nothing to help the UK’s energy security or reduce bills as the oil and gas will be sold on the international market. They will only fuel more floods, fires and droughts around the world.”

Norwegian energy giant Equinor and British firm Ithaca Energy jointly own the Rosebank field.

They said it would create around 1,600 jobs during its construction and support around 450 UK jobs over its lifetime.

Equinor declined to comment while the court challenge was ongoing, but said it was continuing to “work closely with all relevant parties to progress the project”.

He added: “It is vital for the UK and will bring benefits in terms of local investment, jobs and energy security.”

A Shell spokesman said the Jackdaw development was developed in compliance with all relevant agreements and permits.

He added: “Jackdaw is a vital project for the UK’s energy security and the project is already well advanced.

“Stopping work is an extremely complex process with significant technical and operational issues now that the infrastructure is in place and drilling has begun in the North Sea.

“Jackdaw will provide enough fuel to heat 1.4 million UK homes as older gas fields reach the end of production.”

The UK government has previously promised that oil and gas will play an important role in the economy “for decades to come” as the UK transitions to clean energy.

The Scottish Government has previously said it has a “presumption against” new oil and gas exploration.

However, Prime Minister John Swinney said in June that it would still be needed “for some time” to help the country reach its net-zero goals by 2045.

Both governments said it would not be appropriate to comment on legal proceedings live. The NSTA also declined to comment on a live case.

Comedian Frankie Boyle was due to moderate a public meeting of around 150 climate change campaigners in Edinburgh on Monday night after lending his support to the Stop Rosebank campaign.