The New York attorney general filed a lawsuit against the American government for failing to carry out an environmental risk assessment into a controversial new drilling operation known as "fracking" on the same day that it was announced the technique would be suspended in Lancashire.

Eric Schneiderman's case aimed to force the government to carry out a risk assessment on the contentious drilling, in which fluids are pumped under high pressure deep underground to blast apart rock and release natural shale gas. This came four days after a second earthquake near Blackpool, which may have been triggered by the process. The tremor on Friday occurred as energy firm Cuadrilla Resources was extracting gas.

Fracking is highly contentious in America, where gas has leaked into the water supply, and is now drawing criticism from across the UK.

Brian Baptie of the British Geological Survey (BGS), said: "The timing of these two events in conjunction with the ongoing fracking at the site suggests that they may be related. It is well-established that drilling like this can trigger small earthquakes."

Yesterday, campaigners in Wales said the quake was further reason for shale gas test-drilling in south Wales not to go ahead. Louise Evans, of the campaign group Vale Says No, said: "It's extremely worrying. I think Vale councillors should take notice."

Mr. Schneiderman argued that the American agency should not be using the technique before carrying out a comprehensive environmental impact study. The lawsuit claims an assessment is required by federal law.

"Before any decisions on drilling are made, it is our responsibility to follow the facts and understand the public health and safety effects posed by potential natural gas development," Mr. Schneiderman said.

While bans on commercial fracking are already in place in France, New York and Pennsylvania, Cuadrilla said that that it may resume fracking operations at its site near Blackpool in forthcoming weeks.