The head of the UK Environment Agency has given his public backing to a gas fracking boom in the UK, despite concerns over methane emissions, underground water pollution and 'industrialisation' of the countryside.

New drilling techniques, known as fracturing or fracking, are allowing companies to exploit underground gas reserves. However, the boom in gas extraction in the US has been linked to a host of environmental problems, as shown by the Ecologist Film Unit's investigation from the US in 2010.

Since drilling testing began in Blackpool in 2010 fracking sites have sprung up across the UK, including North Wales and West Sussex, and led to a number of protests. Testing in Blackpool was temporarily suspended last year after it caused a small number of minor earthquakes in the region.

The Department for Climate Change and Energy recently confirmed it wanted to give the go-ahead for fracking to re-start in the UK.

Lord Smith said today the Environment Agency would not block the expansion of fracking across the UK.

'The source of a domestically available gas supply would of course be potentially very beneficial for our energy needs. It would provide energy security which we don’t necessarily have [cheaper gas] when we have to import gas from abroad – it could be affordable.

'However, there are two very, very big IF’s. The first IF is that it has to be drawn out of the ground effectively and safely. That means worrying about the way in which the drilling takes place; it means worrying about making sure that methane is captured rather than discharged into the air and it means making sure that none of the contaminated water gets into the ground water that sometimes can fill our water supply.'

Lord Smith's backing follows pressure on the UK to suppoer the extraction of shale gas. Former BP chief Lord Browne said last month that the Government should not 'get in the way' of shale gas companies such as Cuadrilla Resources, of which he is now a director. The British Geological Survey (BGS) estimate the UK could become one of the world's biggest shale gas producers.

Lord Smith also admitted that he had changed his mind over nuclear and now supported new power stations being built in the UK. 'Twenty years ago I would have said over my dead body over nuclear power. Now, climate change has made a realist of many of us and I have to say it has to be part of the mix.'