Companies hoping to exploit a reportedly massive underground shale gas field under Lancashire will face minimal regulation, despite using controversial extraction methods, an exchange of letters with government agencies has revealed.

A lack of government regulation has been widely blamed for explosions and pollution in the US, where hydraulic fracturing or "fracking" is taking place in some areas on the scale envisaged for Britain by Cuadrilla Resources. The company this week announced they had discovered 200tr cu ft of shale gas below Lancashire, and the possibility of drilling thousands of gas wells.

Environmentalists and engineers fear that shale gas extraction could potentially devastate water supplies near where fracking takes place, because methane or chemicals used in the process could leak into ground water.

But a series of letters seen by the Guardian between the company, a former oil and gas engineer with experience of fracking, and officials in the Department of Energy and Climate Change (DECC), the Environment Agency (EA), and the Health and Safety Executive (HSE), shows that no government body has overall responsibility for monitoring the nascent industry.

The letters show:

• Government inspectors from three agencies have made only two random and a handful of pre-arranged visits to Cuadrilla's exploratory operations since work began 18 months ago.

• The government has no specific regulations on "unconventional" gas exploration located within hundreds of metres of settlements. It is relying on old regulations developed for offshore wells.

• No environment impact survey has been conducted by the EA or Lancashire County Council.

• No study has been released on the possible links between the small earthquakes that took place in Lancashire and the fracking operation being carried out by Cuadrilla at the time.

• Confusion between the DECC, EA and HSE, the three government agencies which each have different responsibilities.

• The recent energy and climate change select committee inquiry into shale gas did not consider tightening regulations, citing a lack of resources.

• Companies are not expected to monitor, measure or analyse the polluted liquids that come back up the boreholes and must be disposed of elsewhere.

• The government has not conducted any analysis on the impact of fracking on climate change and the renewable energy industry.

Environmental concerns centre on the release of methane and the potential for the chemicals used in wells to contaminate water, either through the cracks forced open in the rocks by the fracking process, explosions from the release of methane gases, or through drilling bores through aquifers.

Robert Howarth, professor of ecology and environmental biology at Cornell University, called for a moratorium on drilling: "The best evidence indicates widespread contamination of drinking water wells within 1km of gas wells. A moratorium is necessary to step back and better study the risks to water quality, air quality, and global warming. Only once such studies are completed can society begin to analyse what sort of regulation might be sufficient."

France, Switzerland and several US states have banned fracking, but British ministers and officials in the DECC insist no additional regulation or delay is needed.

There is also confusion about how the Caudrilla operation will be overseen. Donald Dobson, HSE's head of discipline, well engineering, says in a letter to former oil and gas engineer Mike Hill, that it is financially impossible to check each well. "Verification of an individual well is not the role of the HSE. The resource implications would be immense."

There is also disagreement between officials at the EA over how many times Cuadrilla has been visited randomly. In one letter, Mark Goucher, an EA customer services operator, says that all of its eight sampling visits "have been unannounced". But Stuart Mcdonald of the agency says. "We have made one unannounced out of eight sampling visits." By contrast, Cuadrilla chief executive Mark Miller says: "The EA makes random visits two to three times each month."

Equally, the HSE considers fracking to be low-risk and has only made one site visit. "To date, HSE has conducted one site inspection of Cuadrilla's UK operations. We do not generally make unannounced site visits," says Dobson.

Tim Yeo, chair of the Commons energy select committee that investigated shale gas exploitation earlier this year, accepts that there is a potential conflict of interest if companies self-monitor: "We concluded that while there is a risk of conflicts of interest affecting the judgement of independent competent persons (ICPs) who assess the design of wells, we had no evidence of such conflicts presented to us," he wrote.

Hill, who has worked on fracking operations in the US and Africa, said: "We are all relying on companies to monitor themselves. This is totally unacceptable. I know the pressures that can be brought to bear. It is not an acceptable excuse to put all responsibility on an examiner that is in fact being paid for by the exploration company.

"Without strong regulation we are in the same boat as the US was from 2005 when Dick Cheney exempted [fracking operations] from the Clean Air Act and Clean Water Act. Nobody is exempt here but at the same time with no regulation we potentially face the same horrors as the US – the same serious risks to public health and the environment," said Hill.

Cuadrilla is known to want better regulation, both to reassure local communities and to prevent cowboy operators abusing the system. Miller accepts that more checks should be done on the cement casings of boreholes, and in one letter says he is now considering doing this even though the authorities do not demand it.

Engineers contacted by the Guardian said self-regulation was not enough to avoid problems. "If ever an industry needed tight regulation then this is it," said one. "What about verifying the well design? What about ensuring no flow of gasses or liquids up to the surface? What about asking for the cement bond logs to be done, [something] even the exploration company thinks is necessary."

But in article for the Guardian this week, the energy and climate change minister Charles Hendry played down the need for stronger regulation. He said: "In the UK, shale gas operations are regulated by the same rigorous regime that all oil and gas operators must adhere to.

"Each application must go through the local planning application process and before any drilling occurs proposals must also be scrutinised by the Environment Agency to make sure there is no risk to the environment, and in particular to water sources; by the HSE for safety; and by my department to ensure best use is made of the resources."