British exploration company IGas Energy on Monday said it believed it was sitting on a far bigger amount of shale gas than thought, ahead of controversial drilling work to begin this year in northwest England.

The findings of IGas data published in a statement revealed a gas volume ranging from 15.1 trillion cubic feet to 172.3 tcf, with the 'most likely' amount standing at 102 tcf.

The company's previous estimate last year had put the lowest amount at about 9.0 trillion cubic feet for an area covering 300 square miles (777 square kilometres).

"The announcement of the gas in place volumes of up to ca. 170 tcf in our northwest acreage follows the completion of a very thorough study by the IGas technical team and supports our view that these licences have a very significant shale gas resource with the potential to transform the company and materially benefit the communities in which we operate," said IGas Energy chief executive Andrew Austin.

"The planned drilling programme, commencing later this year, will further refine these estimates and advance our understanding of this shale basin," he added in the statement.

The British government in December came out in favour of a controversial shale gas extraction method known as fracking, saying that work should be resumed even though it is suspected of having triggered earthquakes.

Hydraulic fracturing or fracking is the drilling of underground shale rock formations by injecting chemicals and water to release trapped natural gas.

Opponents say it causes water pollution but energy groups say it provides access to considerable gas reserves and drives down energy prices for consumers.

North America is experiencing a boom in both shale oil and gas production, while last year the International Energy Agency had forecast that the United States would become the world's biggest oil producer by 2017 thanks to shale energy.

In Britain meanwhile, energy firm Cuadrilla Resources was last year forced to halt drilling trials in northwest England after the fracking technique was thought to have caused tremors.