Citing an independent report, exploration company Egdon Resources now estimates that its UK shale gas licences hold around 18 trillion cubic feet of gas, enough to supply Britain for more than 6 years. This is 10 times the previous estimate.

Egdon said it had not assessed the risks of extracting the gas, which meant there was no certainty extraction would be commercially viable. Typically only 10-15% percent of resources in place are able to be extracted.

The UK government is counting on the extraction of huge shale gas reserves to help make up for a decline in North Sea gas production, and has promised tax and local community incentives for exploration.

The company, which sold parts of its shale gas licences to French oil major Total earlier this year, also said it was continuing to look for acquisition and consolidation opportunities in the sector. It added that it plans to participate in Britain's next onshore licensing round, expected later this year.

"Given the high level of interest and recent transactions, we expect our UK shale-gas assets to be an increasing near-term value driver for the business," Egdon chairman Philip Stephens said in a statement.

British utility Centrica and French peer GDF Suez have also entered the UK unconventional gas scene over the past year, paving the way for further interest by major oil and gas companies.