Opponents of shale gas extraction are protesting in London amid reports the government is to green-light the controversial practice, known as fracking.
Campaigners delivered a letter Saturday to Prime Minister David Cameron's 10 Downing Street office calling the extraction of gas by hydraulic fracturing "an unpredictable, unregulatable process" that could poison the environment.
Advocates of fracking say tapping underground gas reserves could transform Britain's energy supply, but critics say the environmental risk is too great.
Cuadrilla Resources Ltd. halted work on Britain's only shale gas project last year after it triggered a series of small earthquakes in northwest England.
The Independent newspaper reports that the government will soon give the go-ahead to much wider exploration.
The government says it is still "too early to assess the potential for shale gas."