British Prime Minister Keir Starmer indicated he would not stand in the way of the Rosebank oil and gas field, after a court blocked it, sending the decision to the government which had pledged not to issue any new licences.
Starmer's government had said it would not issue new licences to explore new fields over fears about climate change, but it had said it would not revoke existing licences.
The future of two projects, Shell's SHEL.L Jackdaw and Equinor's EQNR.OL Rosebank, had been in doubt after a court overturned their approvals in the face of challenges by climate campaigners.
"I can't preempt the decision, but you know, we did say that where a licence had already been granted, we wouldn't interfere with them," Starmer told Sky News on Thursday.
"I'll be open with you, oil and gas is part of the future mix for decades to come."
Equinor and its partner Ithaca Energy want to develop the Rosebank oil and gas field, but developing one of the last known major oil reservoirs in Britain has been a lightning rod for climate activists calling for a halt to fossil fuel production activity.
(Reuters - Reporting by Sarah Young, Editing by Paul Sandle)