With major oil deposits uncovered in England, an advocacy group said it was concerned about the pace of the fledgling shale industry in the country.

U.K. Oil & Gas Investments announced there may be as much as 100 billion barrels of oil onshore in the Horse Hill license area of the Weald basin in southern England.

"Appraisal drilling and well testing will be required to prove its commerciality, but this Weald hybrid play has the potential for significant daily oil production," UKOG Chief Executive Officer Stephen Sanderson said in a statement.

The discovery comes as the country contemplates the future of North Sea production, where older fields are in a steady state of decline. Operating expenses in the North Sea are up 8 percent while revenues for oil companies working in the region are at their lowest levels since 1998.

Brenda Pollack, a regional campaigner for the British Friends of the Earth, said the Horse Hill assessment means hydraulic fracturing may be on the forefront of the national energy agenda.

"Any firm proposing to drill for oil in the region knows it will face huge opposition," she said in a statement.

Some protests against early shale operations in the country turned unruly last year.

For Sanderson, the find could pan out to be one of the largest onshore discoveries made in the country in the last 30 years. Such a major discovery, he told the BBC, holds "national significance."

UKOG estimates the oil reservoir in Horse Hill is analogous to the Bakken shale oil reserve in North Dakota and the Permian basin in Texas, two of the most productive shale reservoirs in the United States.

The company said the reserves at Horse Hill are in shale beds that are fractured naturally, meaning extraction may be carried out using conventional techniques.