The equivalent of more than 160,000 barrels of oil have spilled into the North Sea in the past five years, according to environmental groups.
Data obtained by Oceana UK and Uplift shows 22,326 tonnes of oil were released into UK waters by oil and gas companies between 2017 and 2022.
Some oil spills are allowed in so-called “produced water”.
That is water found within rocks alongside oil and gas and is a by-product of oil and gas extraction. Companies need a permit from the UK Government to release it.
However, environmental groups say around 42% of the spills were not through permits.
The campaigning group Uplift obtained the information through Freedom of Information requests.
Uplift director Tessa Khan said: “The oil and gas industry is an industry that is really operating out of sight and out of mind for the past five decades in the UK.
“This data really shows the range of impacts and harm that’s being caused by this industry on the UK’s seas.”
The environmental groups argue the spills are impacting on marine wildlife, such as dolphins and seabirds.
“We are currently allowing drilling in marine protected areas and that is shocking,” Khan added.
“We shouldn’t allow oil and gas extraction to happen in environments that the government itself recognises has special ecological value.”
Mark Wilson from the industry body OEUK said the sector takes all releases “very seriously, regardless of size or potential for harm”.
He added: “Our latest data, covering 2022, published in our environment report for that year, shows that the amount of oil released in ‘produced water’ fell by 10%.
“For context, the UK annually produces about 40-45 million tonnes of oil and up to 40 billion cubic metres of gas. This equates to just under half the UK’s demand for oil and gas.
A UK Government spokesperson said: “We monitor offshore pollution incidents closely, and we are clear that companies should not be breaching their permit conditions.
“If they do, appropriate action will be taken, including the use of fines.”