Sarah Finch, who is supported by the Weald Action Group, told the Independent that ministers were effectively supporting controversial plans, approved by the Conservative-run county council, to extract oil from four new wells for the next two decades.
The government told the Independent it did not have “any view on the merits of the Horse Hill development”.
Hearings on a legal challenge began at the High Court on Tuesday.
Until 2019, the owners of the Horse Hill oil site only had a licence for short-term drilling.
But in September 2019, Surrey County Council granted planning permission for Horse Hill Developments to expand its operation near Gatwick Airport. The application comprised plans to retain and expand the site, including two existing wells, and to drill four new wells for the production of hydrocarbons for 25 years.
Campaigners argue that the environmental impact assessment (EIA) on which the council based its decision should have taken into account the full consequences for the climate, including greenhouse gas emissions from the combustion of the oil produced at the site.
Campaigner Sarah Finch launched a judicial review in 2020, but this was dismissed in the High Court in January this year.
However, in March the Court of Appeal judge Lord Justice Lewison said that the EIA argument “has far-reaching ramifications” and “the emission of greenhouse gases is a matter of considerable public concern”.
In granting permission to appeal, he added that “although the judge's reasons for his conclusion are cogent, they are open to proper challenge; and in view of the importance of the question, I regard this as a compelling reason for the appeal to be heard”.
The Department for Levelling Up, Housing and Communities (DLUHC) is listed as a party of interest at a two-day Court of Appeal hearing into the validity of the council’s approval process, as the proceedings relate to its National Planning Policy Framework (NPPF).
Speaking outside the Royal Courts of Justice before proceedings opened on Tuesday, Finch said she thought it was wrong “legally and morally” that 20 years' of oil drilling has been permitted in a climate emergency.
“[The council] didn’t consider the indirect emissions that would result from burning the fuel.”
She added that the government’s involvement in the case directly contradicted its climate message at the COP26 climate conference. “Boris Johnson was talking last week about the need to transition away from fossil fuels as quickly as possible. Three days later, the government is defending 20 years of oil drilling, which will take them right up to the net zero deadline,” she said.
UK Oil and Gas PLC, the majority stakeholder in the Horse Hill site, and Surrey County Council both declined to respond to the Independent, saying it would “not be appropriate for us to comment at this stage”.
A DLUHC spokesperson said: “The department’s role in this appeal is in no way an expression of any view on the merits of the Horse Hill development, and concerns only the interpretation of regulations. It would be inappropriate to comment further on ongoing litigation.”