CLIMATE and tax campaigners have joined forces to demand Chancellor Rachel Reeves investigate a deal bringing Shell together with Equinor, the majority shareholder in the Rosebank oil field.

The Aberdeen-based joint venture, Adura, would be the biggest producer of oil and gas in the North Sea and take on Norwegian state-owned Equinor’s 80 per cent operating interest in Rosebank to the west of Shetland — Britain’s largest untapped field at 300 million barrels.

A licence to exploit the field had been granted by the last Tory government, only for it to be struck down by the Court of Session, which ruled in line with an earlier Supreme Court judgement that the lifetime emissions from the oil extracted should have been taken into account in the application.

Equinor has since reapplied, but with a Westminster government decision thought to be imminent, campaigners at Stop Rosebank, Global Witness, Tax Justice UK, TaxWatch and the End Fuel Poverty have jointly written to Ms Reeves, arguing the deal “raises serious questions around the firms’ real motivations.”

The letter called on the Chancellor to “fully investigate the creation of Adura by Shell and Equinor” to assess the “legality” of the deal which they believe offers Equinor “access to income from Shell’s operations as it struggles to get major projects — such as the controversial Rosebank oil field — off the ground,” and will “allow Shell to write off significant tax liabilities on its projects against losses and allowances built up by Equinor.”

Stop Rosebank’s Lauren MacDonald said the deal “shows how our biggest polluters game the system to make it work for them,” but a spokesperson for Shell dismissed the claims as based on “flawed analysis,” insisting Adura was “expected to be a major contributor of tax to the UK government over its lifetime.”

Tax Justice UK’s Faiza Shaheen accused the firms of “creating complex financial structures to dodge billions in tax while they drive us closer and closer towards climate tipping points.

“This merger is a profit-seeking venture for corporations that have already made a fortune from the climate crisis,” she said.

“The Chancellor must make it clear in the autumn Budget that those who pollute the most must pay for the damage they are responsible for.”

The Labour government and Equinor have been contacted for comment.