AN energy firm has its sights set on tapping billions of pounds of gas from coal seams below the North Sea bed after moving to build the UK's first plant to convert underwater coal to gas.

Cluff Natural Resources said vast coal reserves are available in undersea seams around Scotland and its scheme planned for the Firth of Forth alone has the potential to produce enough energy to power 150,000 homes over a period of at least 15 to 20 years.

The London-based company has eight offshore underground coal gasification (UCG) licences for sites around the UK coast - two in Scotland in the Firth of Forth, at Largo Bay and Kincardine - and has just won 11 more licences for energy sites in the North Sea off England.

It signalled further expansion in waters off Scotland yesterday as plans are drawn up to extract coal from under the Firth following the discovery there.

The process sees the coal drilled and mixed with oxygen to produce syngas, which can be used to power boilers, turbines and supplied to petrochemical, steel or chemicals industries.

However, a Green MSP said the move could show "Scotland's coast is up for grabs" and is to raise the issue at the Scottish Parliament.

CNR said a study found as much as 335 million tonnes of coal near Kincardine and the company is seeking permission to build the UK's first deep offshore underground coal gasification project to extract it.

The amount of coal has been confirmed by an independent body and it is claimed the project will create jobs and protect existing ones.

Algy Cluff, CNR chairman and chief executive, said: "This report supports the company's UCG licence selection and forms the basis for future investment in Scotland while proving the performance of the deep UCG process in a UK context.

"The development of UCG at the Kincardine licence area would create jobs, help protect existing industry and create significant supply chain benefits.

"The deep offshore UCG projects being undertaken by CNR have significant environmental safety and, when combined with carbon capture and storage, climate change benefits compared with coal mining and coal-fired power generation."

Andrew Nunn, the company's project manager, said the latest 11 sites secured represented a "double" opportunity for oil and gas and also coal gasification energy with future further expansion north. He said the current project could take six years to complete but a pilot scheme could be set up within two.

There are claims previous projects in America, Australia and India led to water contamination caused by the process, which involves drilling a borehole into a coal seam, flushing it with oxygen and igniting it with a burner to produce gas.

Green Party MSP Alison Johnstone said she would raise the issue at First Minister's Questions.

She said: "Many people will be shocked to learn of the extent of the underground coal gasification industry in Scotland, and will be seriously concerned at the prospect of drilling on their doorstep.

"If Cluff get permission to press ahead under the Forth it will send a terrible message that our coast is up for grabs and it will set us back in our journey towards a successful low carbon economy."

Lang Banks, director of environmental charity WWF Scotland, said Scotland needs to rely more on electricity and renewables rather than coal and gas.

He said: "Plans to 'burn' coal under the Firth of Forth will not deliver that aim and should be a complete non-starter.

"In a worst-case scenario, proposals such as this one could even extend our use of fossil fuels, locking us into a high carbon world."

Energy firm Clean Coal was granted a licence to investigate reserves off the coasts of Dumfries and Galloway five years ago and another, Five-Quarter, has licences for the Firth of Forth.