Billions of barrels of oil have been found in the ground beneath the south of England, according to a report out Friday.

The official analysis by the British Geological Survey (BGS) revealed the scale of energy reserves lying under parts of Sussex, Hampshire and Kent - but it shows that there is far less than had been hoped.

The BGS report, commissioned by the Department for Energy and Climate Change and released this morning, estimates that there are 4.4billion barrels-worth of oil in the ground under the Weald Basin  in Kent and parts of Sussex and Surrey.

How much of this is recoverable is not yet known - further drilling and testing of new wells will be needed to establish this, but the discovery is set to spark a new stage in the battle between environmentalists and energy firms over the controversial topic of fracking.

Green MP Caroline Lucas condemned news of the findings as 'disastrous' from a climate change perspective in general, and for those living in the south east in particular.

Today's RGS report estimates that the Weald Basin, a vast area covering around 3,500 square miles in the south, could contain between 2.2-8.5billion barrels of oil, equivalent to 290-1,100million tonnes.  This is a disappointment compared to hopes that it might contain as much as a third of the oil discovered in the North Sea.

Currently Britain consumes around 500million barrels of oil per year.  The new report says that a 'resonable estimate' of what may lie in the Weald Basin is 4.4billion barrels - roughly a tenth of what has been recovered from the North Sea in recent years.

But news of the large deposits - about a tenth of what has been recovered from the North Sea in recent years - will have implications both for politicians keen to extract it and for Britain's long-term energy market.

The revelation comes just weeks after the Mail revealed ministers are preparing controversial plans to change the trespass law, giving energy firms the right to frack beneath homes and private land without the owners' permission.

Today, the Government announced a consultation on proposals to 'simplify' the existing procedure to extract shale gas and oil.

Under the new plans, energy firms will be allowed to dig 1,000ft (300m) down for shale gas and deep geothermal operations provided they notify local communities and give them a 'voluntary community payment' for access to the land of £20,000 per well.

Business and Energy minister, Michael Fallon, said: 'Britain needs more home-grown energy. Shale development will bring jobs and business opportunities.

'We are keen for shale and geothermal exploration to go ahead while protecting residents through the robust regulation that is in place.

'These proposals allow shale and geothermal development while offering a fair deal for communities in return for underground access at depths so deep they will have no negative impact on landowners.'

Professor Richard Selley, from Imperial College London, said earlier this year that the discovery of oil in the Weald 'should not be a surprise'. There are already a number of oilfields around the North and South Downs which have been known about for decades.

Geologists poured cold water on excitement about how much oil might be recoverable, with some saying as little as five per cent of the total resource - 220million barrels - might be available for extraction.  This would equate to just 0.5per cent of the 40billion barrels pumped out of the North Sea in recent years.

Energy expert Professor Stuart Haszeldine, of the University of Edinburgh, was among those warning that oil from the Weald Basin wouldn't last long.

He said: 'From the estimated 4.4billion barrels, I would expect maybe 400million barrels could be extracted, which is the equivalent of one North Sea oil field.

'The UK uses 500million barrels per year, so it's a lot of bother for one year's supply.'