UK Oil & Gas Investments (UKOG) said the Horse Hill-1 well in the Weald Basin, north-west of London, is now thought to hold 158m barrels of oil per square mile.

In May 2014, the British Geological Survey estimated the Weald Basin to hold around 4.4bn barrels of shale oil.

Stephen Sanderson, the chief executive of UKOG described the find as a possible "world class" resource with the potential for "significant daily oil production."

He said: "Drilling the deepest well in the basin in 30 years, together with the ability to use concepts, techniques and technology unavailable in the 1980s, has provided new cutting-edge data and interpretations to comprehensively change the understanding of the area's potential oil resources."

The US-based firm which studied the reservoir estimated that recovery of the oil would be limited at between 3 percent and 15 percent of the total.

It also suggested there was no need to use the controversial extraction process, known as fracking, to get access to the oil.

Mr Sanderson said: "The company considers that the high pay thickness, combined with interpreted naturally fractured limestone reservoir with measurable matrix permeability, gives strong encouragement that these reservoirs can be successfully produced using conventional horizontal drilling and completion techniques."

The UK currently produces 770,000 barrels of oil per day, compared to 11.1m in the United States and 11.7m in Saudi Arabia.