Fracking explained: What is it and why is it so controversial?

The government has been accused of a major u-turn on fracking after MPs approved plans to allow the controversial process to take place under national parks and other protected areas.

The move has been met with anger from campaigners, who claimed the plans would put the environment at risk.

Many, however, see it as a cheap, home-grown energy source that could bring UK consumers' bills down.So what is fracking? And why is it such a contentious issue?

  • How fracking works

Fracking is short for hydraulic fracturing. It is a process whereby liquid is injected at high pressure to force open existing fissures in rock, releasing the natural gas trapped in shale formations.

A mixture of water and chemicals is then pumped in to ensure the cracks remain open, ensuring a steady flow of shale gas to the surface.

  • When will fracking begin?

Fracking could take place under national parks due to new legislation. Credit: PA

Fracking is not currently taking place in the UK - current drilling is only exploratory.

However, there are a number of a parts of the country that have been identified as potential sites where large reserves of shale gas could be found.Among them are national parks and sites of special scientific interest, under which drilling will be allowed after a parliamentary vote - as long as it takes place outside protected areas.

Dozens of fracking licenses have been handed to companies. All of them will have to receive planning permission from local councils before they can go ahead with any drilling.

However, the government will make a final decision after Lancashire County Council rejected applications from Cuadrillia to frack at two sites - Roseacre and Little Plumpton.

  • Where would fracking take place?

A map of potential UK fracking sites. Credit: OGA

Large parts of England - particularly in the north - have been earmarked as potential sites for shale gas exploration.

Around 6,000 square miles of land has been earmarked for possible drilling - with this interactive map showing where it could take place.

While a number of licences have been issued in Wales and Scotland, these are currently off-limits after the governments of both countries issued a temporary ban on fracking.

  • What are the arguments in favour of fracking?

Fracking is viewed by some as a cheap and plentiful UK energy resource. Credit: Peter Byrne/PA Wire

Those in favour of fracking view it as an easy and potentially lucrative win - particularly for the UK.

Amid a shortening global supply of fossil fuels, Britain is estimated to have an enormous supply of untapped shale gas reserves - potentially as much as 1,300 trillion cubic feet in the north of England alone, according to a 2014 study by the British Geological Survey.

New technology has made accessing these shale gas reserves possible for the first time, though experts are in disagreement over how much could potentially be extracted.

Either way, pro-frackers say the potential for a home-grown source of cheap energy is too good to turn down.

  • So why are so many opposed to fracking?

Anti-fracking campaigners in Lancashire. Credit: Lynne Cameron/PA Archive

Campaigners opposing fracking cite a number of concerns - among the most popular being fears about possible contamination of water supplies, the potential for earthquakes and, more simply, the large number of lorries needed to transport materials to and from the sites.

Many fear that the methane gas and toxins pumped into the drilled holes can leak into the water supply, making it potentially dangerous to drink.

Fracking is also deemed the likely cause of two minor earthquakes in Blackpool - though it is unclear if these should be expected at other sites.

On a broader scale, campaigners argue that investing in gas exploration is incompatible with the global effort to reduce fossil fuel reliance, and claim that fracking will not bring down energy bills as much as promised.

  • Where do UK politicians stand on fracking?

Energy Secretary Amber Rudd is committed to delivering fracking. Credit: PA

The Conservatives have promised to deliver fracking projects, and efforts to hasten their introduction appear to have picked up since the party won a parliamentary majority in May.

Labour has said fracking should not go ahead in Britain "until stronger safeguards are in place to protect drinking water sources and sensitive parts of our countryside like national parks".

The Liberal Democrat leader Tim Farron has promised to oppose fracking and the SNP has banned fracking in Scotland until it knows more about the impact.

Plaid Cymru has also called for a moratorium on the technique, while the Green Party is fully opposed to it.

Ukip has previously supported it, with its sole MP Douglas Carswell