Decision due on Scottish coal gas
Greens calling for an outright ban on the technique here
Any announcement "short of an outright ban" on underground coal gasification (UGC) will be viewed as a failure by the Scottish Government to stand up to the oil and gas industry, the Greens have said.
Energy minister Paul Wheelhouse is due to give a statement on the issue at Holyrood today following the submission of an independent review.
The Scottish Government imposed a moratorium on UGC in October last year to consider the impact of the gas extraction technique.
Campaigners - who say UCG could cause significant environmental harm - are hopeful Mr Wheelhouse will announce an outright ban.
The Conservatives said he should instead "send a clear signal" that Scotland is open to new energy technology.
Scottish Greens MSP Mark Ruskell said: "Anything short of an outright ban on underground coal gasification will be deemed as an environmental failure of the government to stand up to pressures from the oil and gas industry and instead fully commit itself to a renewables future."
Scottish Conservative energy spokesman Alexander Burnett said: "As with fracking, underground coal has the potential to create thousands of jobs and boost the economy at a time when the North Sea oil and gas industry is in decline.
"The minister has the opportunity to send a clear signal to investors that Scotland is open to business opportunities from new energy technologies.''
Energy firm Cluff Natural Resources had been planning to use UCG to extract gas from under the Firth of Forth near Kincardine, Fife, and had secured licences from the UK Government's Coal Authority.
The company halted work on the project last year until the political debate on the issue was resolved.
After the moratorium was imposed, the Government tasked Professor Campbell Gemmell, former chief executive of environmental agency Sepa, with carrying out an independent examination of the technology.
UCG licences in the Firth of Forth and Solway Firth were also held by firm Five Quarter, although the company collapsed earlier this year.
Friends of the Earth Scotland's head of campaigns Mary Church said: "Setting coal seams under two of our major firths alight is a reckless idea and we urge the government to listen to communities, act decisively and make sure underground coal gasification never takes place in Scotland.
"The climate change consequences of permitting UCG are enormous and allowing the industry to take root would be completely out of step with Scotland's world-leading ambition to tackle global warming."
WWF Scotland director Lang Banks said: "Burning coal underground should have no place in Scotland's energy future, which is why the Scottish Government was right to extend its moratorium on unconventional gas extraction to include underground coal gasification.
"We hope the minister's announcement will turn the current moratorium into an outright ban.''
A Scottish Government spokesman said: "Following the submission of Professor Campbell Gemmell's independent review of underground coal gasification, minister for business, innovation and energy Paul Wheelhouse will make a statement to update parliament on Thursday October 6."