The government of Prime Minister Keir Starmer of Britain finds itself in a quandary. It came to power promising to lead a clean energy boom that it said would revive a stagnant economy and protect consumers from energy price surges that were driving up inflation.

Yet it also seems wary of setting off a collapse of the oil and gas industry in the North Sea that sustains an estimated 120,000 mostly well-paid jobs and produces much of the natural gas that keep British businesses and homes humming.

“While we make that transition, the oil and gas industry will play an important role in the economy for decades to come,” Britain’s energy minister, Michael Shanks, said this year.

Already there is unease about a sharp slowdown in investment among energy companies and what strikes some as indifference on the part of Britain’s new government, led by the Labour Party, to the potential consequences.

Britain has “been a leader in offshore development,” said Gregor Scott, managing director of Ocean Installer, which does underwater work. “We won’t maintain that forever if there is a dwindling amount of work.”

In the coming months, the government will face a tricky balancing act of pursuing its clean energy agenda while supporting an industry that the country still relies on for energy and jobs.

The importance of oil and gas quickly becomes apparent on a visit to Aberdeen, a port city in the northeast corner of Scotland. Powerful, low-slung vessels move in and out of its harbor, carrying food and equipment to the oil platforms in the North Sea. To the northwest, a procession of large helicopters ferries crews to the oil fields and back.

Aberdeen’s long, dark winter days and a somewhat remote location have not kept Fennex, a technology company, from recruiting university graduates to use artificial intelligence in order to better manage risk in hazardous offshore oil and gas operations.

“We’re passionate about this region and the opportunities it offers,” said Nassima Brown, a former drilling engineer who founded the company with her husband, Adrian.

Britain’s petroleum production has been falling for around a quarter-century, from the time the country was a substantial producer, pumping nearly three million barrels of oil a day, more than Middle East stalwarts like Iraq and the United Arab Emirates. By 2023, its oil output had diminished to 715,000 barrels a day, according to the Statistical Review of World Energy.

Even with the fall, Britain’s output of oil and natural gas, which remains a mainstay for generating electric power, amounted to more than half of domestic consumption, an important consideration at a time of heightened energy concerns since Russia’s invasion of Ukraine in 2022.

Depletion of resources has been a crucial factor behind the drop in production, but government policy has also played a role, especially in recent years.

Linda Cook, chief executive of Harbour Energy, Britain’s largest petroleum producer, said the differences between Britain and other countries, including Norway, were “pretty stark.”

Britain’s government, she added, “sends mixed signals to the sector as to whether or not they’d like additional further investment in domestic oil and gas.”

Britain has taken steps that weigh on investment. The government responded to the sharp rise in oil and gas prices after Russia’s invasion of Ukraine by imposing a so-called windfall tax on energy company profits, a measure it later increased and extended until 2030, even though prices have declined substantially.

Some industry executives were encouraged when the government seemed to heed their pleas to not tighten taxes on oil and gas further in the presentation of its budget this fall. “I think that was a really positive set of discussions over a few months,” said Louise Kingham, senior vice president for Europe and head of Britain for BP, the London-based energy company. “We have more work to do,” she added.

But they are waiting to see what tax strategy the government will pursue after 2030. The Labour Party is contemplating how to comply with a June court ruling that said the licensing process for new oil and gas projects needed to weigh the effect of their emissions. And it is also pondering how to enact its election campaign promise not to issue any new oil and gas licenses.

Adding to the uncertainty, environmental activists have gone to court to try to block two major new petroleum developments, including one called Jackdaw in the North Sea, where Shell, Europe’s largest energy company, has already spent about 750 million pounds.

Oil executives do not seem reassured. Patrick Pouyanné, the chief executive of the French company TotalEnergies, one of the largest producers in British waters, said in October that he had told his North Sea team to halt exploration. “With this political landscape you are not even sure that even if you find something you will be able to, to develop it,” he said at an investor conference.

Only three exploration wells have been drilled in the British North Sea this year. In fact, oil producers have stopped most discretionary expenditure in Britain. Capital investment has fallen to $4.8 billion in 2024 from $27 billion in 2014, according to Wood Mackenzie, a consulting firm.

“There are quite a few other places in the world that are offering similar or even more interesting geological opportunities with a lot lower political risk,” said Graham Kellas, a senior vice president for fiscal research at Wood Mackenzie.

Other signs of companies’ reluctance to invest are emerging. A group of oil companies have put the brakes on an estimated $1 billion project called Buchan Horst in the North Sea off Scotland that would have created hundreds of jobs.

“Who wants to take long-term investment decisions where we’re not sure whether or not we will be able to meet the environmental requirements, or that the fiscal regime will be suitable?” said David Latin, chairman of Serica Energy, which owns 30 percent of Buchan Horst.

Last Thursday, Shell and Equinor, the Norwegian energy company, said they would combine their British oil and gas operations in what appeared to be an effort to reduce costs. Other large oil companies like Chevron and ExxonMobil have already sharply reduced their British North Sea presence.

Even BP, the London-based giant, has scaled back. “The North Sea is not particularly material to us anymore,” said Murray Auchincloss, the company’s chief executive, estimating that it brought in 4 percent of overall cash flow.

Paul de Leeuw, director of the Energy Transition Institute at Robert Gordon University in Aberdeen, said that an orderly decline of output would offer a better shot to achieve “a seamless transfer from one industry to another industry.” But evidence of the dangers of climate change “put a huge amount of pressure on governments and society to go fast,” he said.

To the work force, what the government paints as a bright future in areas like offshore wind and hydrogen looks murky at best.

“Nobody knows what the jobs are going to be,” said Kyle Griffiths, a painter on an offshore platform. “Nobody knows what they’re going to need yet.”

Some businesses are beginning to work in renewable energy areas. For instance, Fennex, the tech company in Aberdeen, is moving into offshore wind. The oil and gas industry is nurturing a “new Aberdeen” of high-tech energy entrepreneurs and workers, said Ms. Brown, the company’s co-founder.

Alternative energy technologies, though, are still in relatively early stages, and it is not clear how many people they will employ.

“The scale of renewables isn't quite there to allow it to be an easy and swift transition for that work force,” said Sandy Bonner, executive president of Bilfinger UK, an engineering company, which has around 1,500 people working on North Sea oil platforms. Mr. Bonner noted that some of those installations have crews of up to 200 people, while near-shore wind farms are maintained by no more than 12.

Still, businesses that have been sustained by the oil industry for decades are preparing for what they see as its inevitable fading. The Port of Aberdeen recently completed a new £420 million harbor to attract cruise ships and renewable energy vessels.

In 2023, though, oil and gas vessels docking at the port still brought in more than half of its revenue. Offshore wind vessels accounted for only around 1 percent.

“Oil and gas is not yet in its decline, despite the politicians’ best attempts to kill us off,” joked Kieran Morton, the port’s business development manager.