The Labour party has called for a ban on UK North Sea oil operators burning or releasing gas “except in dire safety emergencies” after data showed the contentious practice of “flaring and venting” in the region is responsible for a coal plant’s worth of carbon emissions each year.

Campaign group Greenpeace UK will on Monday publish a report that for the first time names and shames the oil operators in British waters that are responsible for the most emissions from flaring and venting.

A joint venture between Spain’s Repsol and Sinopec of China is identified as the operator responsible for the most emissions, followed by France’s Total and Royal Dutch Shell.

Norway outlawed non-emergency flaring 50 years ago — but the practice of burning off gas produced together with oil from reservoirs is still common in UK waters.

This is especially the case at older oilfields where the original operators were not concerned about capturing the less valuable gas and in other locations where there are no nearby pipelines to export it, although many of the larger producers such as Shell, Repsol and Total have in recent years committed to tackle the problem as part of net zero targets.

It is also done for safety reasons or for non-routine operations such as testing wells, although Britain’s energy regulator found in a report last year that only about 10 per cent of gas flared in the UK North Sea in 2019 was for emergency reasons only. The World Bank is campaigning for routine flaring to end globally by 2030.

The report by Greenpeace’s investigative unit Unearthed shows that total venting and flaring by oilfield operators in the UK North Sea released emissions equivalent to 20m tonnes of carbon dioxide between the start of 2015 — the year of the Paris climate accord — and the end of 2019. It is based on data obtained via environmental freedom of information requests from the National Atmospheric Emissions Inventory, part of Britain’s business department.

The average annual total of 4m tonnes equates to the same damage caused by a coal-fired power plant, which ministers have promised to phase out no later than 2025.

“Norway tackled this problem in the 1970s, but our government is clearly asleep at the wheel and is failing to regulate the industry,” said Mel Evans of Greenpeace UK.

The data cover those oil companies that operate platforms and excludes others that only hold stakes in fields. They also do not cover flaring per barrel of oil produced, but still shed an important light on the industry’s emissions as it comes under increasing pressure to justify its future against the UK's legally binding 2050 net zero emissions target.

Ministers and the industry are negotiating a North Sea “transition deal”, which is expected to be published soon.

Shadow business secretary Ed Miliband said the government must “stop turning a blind eye” to venting and flaring in anything other than “dire safety emergencies”, adding that it “undermines our international credibility” as the UK prepares to host the UN COP26 climate summit in Glasgow in November.

The UK Oil and Gas Authority, which is responsible for policing North Sea companies, insisted it was taking a “robust stance” on venting and flaring.

It published a report last year that found volumes of gas vented and flared fell between 2018 and 2019, but the regulator added there were “clear opportunities for industry to go further to advance cleaner production”.

The business department said it was working alongside regulators “to ensure this practice is eliminated as soon as possible”, pointing out the UK had signed up to the World Bank’s plan for a 2030 ban.

Repsol Sinopec said it had reduced flaring and venting by more than 34 per cent between 2018 and 2020 and was forecasting a further 10 per cent cut this year.

Total pointed out it had committed to reaching net zero emissions across its global operations by 2050 or sooner, adding that it had set additional “challenging” interim targets in the UK.

Shell said between 2015 and 2019 it achieved a 19 per cent reduction in the overall emissions from its UK upstream business, which included gas vented or flared, adding: “Minimising venting and flaring matters to us and we are working hard to tackle this important issue.”