Developers have suspended oil extraction at a site in Surrey four months after the Supreme Court quashed its planning permission.

Climate campaign group Friends of the Earth, which supported local activist Sarah Finch during the original case, sent a legal letter to Surrey County Council last Tuesday over the “unlawful” continued extraction at Horse Hill, near Horley.

Lawyers for the group urged the council to take immediate enforcement action against the developer, giving it one week to respond.

The council has since said its position is that the ongoing extraction is unlawful, adding that any development on the site is vulnerable to formal enforcement action.

The Horse Hill developer’s owner, UK Oil & Gas (UKOG), confirmed it made instructions to “voluntarily suspend oil production” at the site effective from last Friday, October 25.

Reacting to the move, Niall Toru, lawyer at Friends of the Earth, said: “We are thrilled the developer of the Horse Hill project finally suspended oil drilling at the site.

“This is much owed to the tireless efforts of local activists who have kept up pressure against the development after many years of campaigning. The fact it went unchecked for four months raises serious questions for Surrey County Council (SCC).

“We hope this signals the end of the Horse Hill development once and for all.”

During the original legal battle, Ms Finch – acting on behalf of Weald Action Group – argued that the environmental impact assessment carried out during the planning process should have taken into account the “downstream” emissions produced when the oil was burned – rather than just the direct impact of extracting the oil.

The Supreme Court’s landmark judgement in June ruled that emissions created by burning fossil fuels should be considered for new drilling sites, quashing Surrey County Council’s decision to grant the development planning permission.

But, according to figures from the industry regulator, the Horse Hill site continued to produce oil, with 138 tonnes extracted in July alone – equivalent to 33 barrels a day.

The developer’s parent company signalled that it was engaged in talks regarding a retroactive reinstatement of planning permission for its recent activities.

In a statement, UKOG said its subsidiary, Horse Hill Developments Ltd (HHDL), has been working with the council “to find the most pragmatic way forward to achieve the required planning re-determination”, including site visits.

“It should be noted that the Supreme Court’s decision was not the result of any action, error or omission by the company or its subsidiary, HHDL, and that HHDL has acted as a responsible operator in full regulatory compliance during the six years of production planning consent,” it said.

“A detailed plan for a safe, full suspension of related operations and activities, including the necessary safe emptying and cleaning of storage tanks, flow lines and other process equipment, will be implemented following SCC’s concurrence.”

In a statement on Tuesday, the council said: “Following discussions between the County’s Planning Enforcement and Monitoring Team and the operator, the County is pleased that commercial production of oil at the site has ceased.

“However, discussions remain ongoing in relation to full suspension of the site and as such the County’s planning enforcement investigation remains live.”

Katie de Kauwe, lawyer at Friends of the Earth, said: “It’s jaw-dropping that oil production has continued at Horse Hill for four months after our highest court quashed the planning permission.

“It’s hard to view this as anything other than a developer gaming the planning system and being allowed to get away with it.”

Ms Finch said: “Up and down the country fossil fuel projects have been stopped, paused and withdrawn following the Supreme Court’s important ruling on my case.

“It seems the only place where nothing has changed is Horse Hill itself, where UKOG is carrying on as if nothing has happened.”