A North Sea oil and gas project is being earmarked for approval by the British government as it prepares to host the Cop26 climate conference and urge nations to reduce carbon emissions.
Environmental groups want the Cambo project shelved, claiming it cannot be justified as the planet battles climate change.
Developing the oilfield would also go against an International Energy Agency report that recommended "no investment in new fossil fuel supply projects".
The heavy crude development off the coast of the Shetland Islands would extract 150 million barrels of oil.
But the project will not be covered by the government's climate checklist, which assesses new oilfields' compatibility "with the UK's climate change objectives", The Times reported.
Groups such as Friends of the Earth Scotland say the plan cannot be squared with the goal of reaching a deal at the Cop26 summit on limiting global temperature increases to 1.5°C.
"It would be completely indefensible if ministers were to approve this, especially after the IEA's report," said Caroline Rance from FoE Scotland.
"It is simply not compatible with the science to go ahead with exploiting these fields and the fact that it is even being considered shows the current system is not fit for purpose."
The Cambo project was licenced for exploration in 2001 and 2004 before the checklist was created in March.
The oilfield, about 125 kilometres north-west of the Shetland Islands, is expected to emit nearly 3.5 million tonnes of CO2 equivalents.
At 1,100 metres underwater, it is one of the deepest fields to be discovered in northern Europe.
Siccar Point Energy, of which Shell owns 30 per cent, is seeking government approval for the development.
"We have proactively taken significant steps to minimise the emissions footprint through its design," chief executive Jonathan Roger said.
The project supported the UK's energy transition ambitions, he said, while "maintaining secure UK supply and creating jobs".
The UK's Oil and Gas Authority is expected to approve the drilling despite Britain's pledge to be carbon neutral by 2050.
In the run-up to the Cop 26 summit, being held in Glasgow in November, the UK is trying to secure guarantees from rich countries to help poorer ones, and to lead the climate challenge by example.
In April, Prime Minister Boris Johnson announced Britain would cut carbon emissions by 78 per cent of 1990 levels within the next 14 years.
"We are working hard to drive down demand for fossil fuels but we also know there will continue to be ongoing demand for oil and gas over the coming years," a spokesman for the Department for Business, Energy and Industrial Strategy said.