An energy company has been accused of drilling an underground well beneath greenbelt land in Surrey without planning permission in what could become an important test case for fossil fuel extraction in the British countryside.

Surrey County Council said Angus Energy, which insists it has not broken the law, could now be fined or punished in some other way, although this might just be a "severe warning".

The company said it had only drilled a "sidetrack" from an existing well into shale rocks underneath the Weald near Brockham and that its operations at the site were already covered by planning permission.

While the 'sidetrack' is designed to find oil and does not involve fracking – the controversial process of shattering rocks to release gas – the case could have wider significance if the UK develops a major fracking industry.

That would see a large number of wells drilled into the countryside, each with a number of branch lines extending from a central hub.

If planning permission is not required for each new branch, this would make it simpler for the industry and harder for local opponents to prevent the escalation of activity at each site. If planning consent is needed, the reverse would be true.

Angus Energy said in a statement that it was of the “firm opinion” that the sidetrack “did not constitute a breach of the planning consents”, adding it had been approved by the Oil & Gas Authority, Environment Agency and Health and Safety Executive.

The firm was even more dismissive of suggestions it needed planning permission in a posting on its website in which it asked “what is the fuss about?”.

“The Government’s guidelines make it absolutely clear that the remit of local councils covers the surface impact of the operations including matters such as noise, visual impact and traffic movements,” it said.

“All of our surface work was covered by our planning permission. We work with our local council on many important surface issues that rely on their expertise and requirements.”

The firm said “no new well was drilled”, only what a “sidetrack”. This, it added, “doesn’t need planning permission according to Surrey County Council’s own criteria”.

“Despite having every opportunity at a number of meetings and in extensive correspondence, Surrey County Council has not identified any way in which the sidetrack causes any planning harm,” Angus Energy said.

“Any characterisation that Angus Energy deliberately misled its investors and the public or misunderstood clear advice is offensive, wrong and self-serving.”

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The company stressed it had no plans to carry out fracking at the well, something that has attracted considerable local protests at a number of other sites around the country.

Angus Energy’s confidence that it had not breached planning law was not shared by the council.

The local authority said in a statement: “We were extremely disappointed to find out that Angus Energy has acted without planning permission and contrary to our advice and guidance so we are currently in discussions with them as a matter of urgency to resolve this.”

A council spokesman told The Independent that there was “a possibility” the company could be required to remove the well or 'sidetrack', but he added this was “unlikely” given it was already there.

“They could get punished for what they have done or they could apply for retrospective planning permission,” he said. “They could be fined, there’s a multitude of things that could happen. They might just get a severe warning.”

Hannah Martin, Greenpeace UK energy campaigner, did not comment on the Brockham site specifically.

But she stressed local councils played a "vital role in making sure local people get a say on energy developments that could affect their local environment and quality of life".

"But by overruling local decisions such as on fracking in Lancashire, Ministers have given the impression that councils can be sidelined when it comes to industries with strong government backing," Ms Martin added.

"There is a real risk that energy companies could take this as a tacit permission to ignore local councils and even bypass the planning process.