Image caption Gas is a natural by-product of shale rock

A Commons committee has urged ministers to support plans for controversial shale gas drilling in the UK.

The energy select committee said environmental problems associated with it in the US could be overcome by tight regulation and good industry practice.

But the MPs said the UK government would need to be vigilant to ensure the technology did not pollute water or produce excessive greenhouse emissions.

Environmentalists said MPs should have called for a moratorium on shale gas.

Campaigners want a moratorium until research into allegations about the technology is complete.

Shale gas is significant to the UK in two ways. First, the massive expansion of shale gas in the US and also possibly in China may depress global gas prices and cause countries to favour gas over coal.

Some experts see this as a double-edged sword - low energy prices are a benefit, but might divert investment from the renewables and nuclear essential for the low-carbon future planned by the government.

The second issue over shale gas is one of energy security. The British Geological Survey estimates that onshore shale gas can supply 1.5 years of the UK's total gas needs.

The MPs say this is a useful but not major contribution - and they recommend that the government should encourage the development of offshore shale gas, where reserves may be far higher, albeit more costly to recover.

'Regulation case'

Test drilling for shale gas is currently underway in Lancashire near Blackpool. The company, Cuadrilla, believes that onshore deposits of shale gas in the UK may have been underestimated.

Critics fear this is industry hype, but Cuadrilla says the shale gas seam near Blackpool is so thick that it may not need the horizontal fracking (rock fracturing) characteristic of so many deposits in the US. Cuadrilla says vertical fracking may be achievable in Lancashire.

It is the fracking process - creating tiny explosions to shatter hard shale rocks and release gas 10,000 feet underground - that has caused so much controversy in the US. Some householders claim that shale gas leaking into their drinking supply causes tap water to ignite.

Image caption Some communities see shale gas as a route to local riches, as well as energy independence

The MPs said this looks a case of inadequate regulation. Tim Yeo MP, chairman of the committee, said: "We can't see any evidence that UK water supplies might be at risk from shale gas - if it is done properly," he told BBC News.

"The regulatory agencies have to keep their vigilance and monitor drilling closely - but the area where the fracking is being done is well below the water table so there really should not be an issue."

The other focus of environmental concern over shale gas is greenhouse gas emissions. A study at Cornell University warned that methane leaks from wells could be so high that in some cases the atmospheric warming effect of shale gas drilling might outweigh that of coal. The MPs dismiss this fear, pointing once again to the need for good practice and regulation to prevent leaks.

David Nussbaum, head of the green group WWF, says this is complacent. WWF is calling for a moratorium on shale gas drilling in the UK until the US Environmental Protection Agency has carried out a major report into the practice - probably next year. They also want to see more studies on the climate effects of shale gas.

He told BBC News: "Shale gas is a controversial source of energy. We've got to be very, very cautious before we go gung-ho for shale gas and we believe there has to be very good evidence before we decide this is the way forward."

The government says existing laws are strong enough to deal with the issues raised - and that bids for licences to extract shale gas (as opposed to prospect for it) will be considered in the normal way.

The new source of energy is proving controversial in Europe, with pro-nuclear France in the process of banning shale gas production and Poland, thought to have by far the biggest reserves in Europe, caught in a major industrial debate about whether to concentrate its efforts on coal or gas.

Some analysts warn that the shale gas phenomenon has provoked an unhelpful war of words between the gas and renewables industries, which complement each other in a way that nuclear power does not.

The argument runs that gas will be needed as a relatively low-cost transition technology, filling in the generation gap when the wind drops. Nuclear power, on the other hand, competes with wind because it produces baseload electricity that needs to be used.