The UK's fledgling shale gas industry could be stopped in its tracks after dramatic new evidence established a link for the first time between the "fracking" technology used to dislodge natural gas trapped in rocks and water pollution.
A study by the US Environmental Protection Agency (EPA) into hydraulic fracturing reported finding a host of chemicals in the groundwater around shale gas wells in Wyoming state.
These included petroleum hydrocarbons such as benzene, and tert-butyl alcohol, a fuel additive, which is among the more than 500 chemicals that are typically mixed with sand and water and blasted into shale to fracture the rock and release the gas.
The EPA findings will put further pressure on the UK Government as it considers whether to allow fracking to become commonplace in this country.
The process has been banned in a number of areas, including France, Switzerland and New York state.
The UK's sole operational fracking site, near Blackpool, was suspended in June following complaints from locals about two earthquakes in April and May. The subsequent report into the seismic activity and fracking concluded last month that it is "highly probable" that there was a connection.
Furthermore, the report established that the fracking activity – by Cuadrilla Resources, a company backed by the former BP chief executive Lord Browne of Madingley – was responsible for a further 48 earthquakes.
The Department of Energy and Climate Change (DECC) is reviewing the report into the Blackpool earthquakes before deciding whether to allow the Cuadrilla site – at Preese Hall in Lancashire – to reopen and other sites to begin fracking.
A DECC spokesman said: "No decision on the resumption of these hydraulic fracture operations will be made until the implications of this [Cuadrilla earthquake] report, and of any further analysis which may prove necessary, has been fully considered."
DECC is expected to decide whether to allow fracking to proceed in the UK early next year.
Commenting on the EPA report, Caroline Lucas, MP for Brighton Pavillion and leader of the Green Party, said: "The Government should halt operations until we have a thorough and fully independent investigation into the environmental and health impacts of fracking."
Although the report into fracking in the town of Pavillion, Wyoming, was unable to definitively prove the link between the controversial process and water pollution, it concluded "detection of high concentrations of benzene, xylenes... in ground water samples from shallow monitoring wells near pits indicates that pits are a source of shallow ground water contamination in the area of investigation".
Encana, Canada's largest gas company and owner of 123 wells in Pavillion, dismissed the EPA report as "not a definitive conclusion".
For its part, the EPA acknowledged that fracking conditions differ from area to area, with issues such as the depth of activity and proximity to aquifer's affecting the chance of possible pollution.