Boris Johnson has insisted that “we can’t just tear up contracts” as campaigners urged him to block the Cambo oilfield project, west of Shetland.
Industry regulators the Oil and Gas Authority and the Offshore Petroleum Regulator for Environment & Decommissioning are assessing plans for developing the Cambo field, submitted by Siccar Point Energy and Shell.
If the field development plan is rubber stamped, around 150-170 million barrels would be produced during the first phase.
Cambo already has a petroleum licence awarded to it during a previous licensing round and exploration and appraisal work has been carried out.
But more than 80,000 people have now signed a petition delivered to Downing Street, demanding the Prime Minister stops the development and blocks any extraction of fossil fuels given the climate crisis and pledges to reduce carbon emissions.
Mr Johnson was challenged about the situation during a visit to an offshore wind development in the Moray Firth.
The Prime Minister told broadcasters: “This was a contract that was signed in… was agreed in 2001 and we can’t just tear up contracts, there is a process to be gone through.
“But what we need to do is use this incredible potential of wind power, and turbines like this… they’ve only been going up in the last four or five years, the size that you’re looking at now, and they’re going to get even bigger.
“So the potential is absolutely enormous. We can power millions and millions of homes across the UK.”
Mr Johnson’s comments came a day after he appeared unaware of the controversy around the Cambo field when he was asked about it on Wednesday.
Business and Energy Secretary Kwasi Kwarteng, who joined Mr Johnson on a visit to the wind farm, previously insisted he was not involved in the decision to allow the fossil fuel extraction.
Labour leader Sir Keir Starmer on Wednesday said the Cambo oilfield should not get the go-ahead and called for a “hard-edged” timetable to end oil and gas extraction.
In addition to the 80,000-strong petition, an open letter signed by 77 organisations has also been sent to Mr Johnson, similarly calling on him to reject the Cambo proposal.
Signatories include Save the Children, RSPB, Oxfam, 350, Friends of the Earth, Green Alliance, Avaaz and Uplift.
The letter says: “As the host of Cop26, it is vital for the UK’s international leadership credentials on climate change for it to walk the walk on all aspects of domestic energy policy.
“The Government has succeeded in mobilising the G7 behind the 1.5C target, which we strongly support. However, approving the Cambo Field will threaten this progress and stall our efforts at climate diplomacy at the exact moment we need them to accelerate.
“It will be hard to avoid the irony of world leaders meeting in Glasgow to discuss how to achieve a 1.5-degree world, while the UK Government contemplates a new oil field just over 300 miles to the north.”
Caroline Rance, from Friends of the Earth Scotland, said: “If the Oil and Gas Authority is going rogue and just nodding these massive projects through, then the Prime Minister has to personally get a grip on energy policy and put a stop to these developments.
“The Government should be supporting and retraining oil and gas workers to transition to jobs in sectors such as renewable energy or decommissioning oil platforms.
“A managed phase-out away from oil and gas is necessary to create the long-term protection for people who currently work in this industry, their communities and the climate.”