TEST drilling for unconventional coal and gas has been given the go-ahead as part of an 18-month process to determine whether industrial-scale fracking should be allowed in Scotland.

A detailed research programme into the potential benefits and possible risks of unconventional fossil fuel extraction will be carried out between now and next summer, ministers announced, pushing a decision on the controversial technology back until after the election.

It will be followed by a four-month public consultation, allowing ministers to reach a decision after the Spring of 2017.

Details of the timetable were announced as Energy Minister Fergus Ewing bowed to pressure from within his own party and extended the existing moratorium on shale gas fracking and coal bed methane extraction to cover a third technique, underground coal gasification, or UCG.

A separate study into UCG will be conducted by Professor Campbell Gemmell, a former head of pollution watchdog SEPA.

A major protest against plans to employ UCG beneath the Firth of Forth is planned for Sunday.

The demonstration is backed by grassroots SNP members opposed to unconventional coal and gas, who have formed a pressure group called SMAUG.

Environmental campaigners Friends of the Earth welcomed the extended moratorium and lengthy decision-making process, and said they were confident it would result in a "full ban" on fracking.

However, they voiced concerns about the start of test drilling, which will be permitted as part of the research exercise.

The Scottish Government, which has previously refused to say whether test drilling would be allowed, said it would require planning consents and must take place "in collaboration" with an independent academic body with research as the "key driver".

But Dr Richard Dixon, director of Friends of the Earth Scotland, said: "If companies end up paying research bodies to take part in test drilling, that would raise questions about the validity of the moratorium."

Ineos, the Grangemouth-based petrochemicals giant which has bought up extensive fracking rights across central Scotland, said it "remained supportive" of the Scottish Government's approach.

A spokesman added: "Ineos also welcomes the understanding that science based evidence gathering will also involve the need for physical testing during the moratorium."

A source said the company was pleased to see a timescale for a final decision.

Mr Ewing first announced a study and public consultation on fracking in January, when he imposed the moratorium.

It came six months after an expert scientific panel set up by the Scottish Government concluded that "significant" shale oil and gas resources could be extracted safely and would provide an economic boost.

The new study will look into the possible economic and environmental impact of fracking and consider "decommissioning and aftercare".

Announcing the process, Mr Ewing said: "We should never close our minds to the potential opportunities for Scotland from new energy technologies but we must also ensure that community, environmental and health concerns are all fully taken account of.

"The research we propose in this timetable will give all interested stakeholders important information to allow a more informed debate during the public consultation."

Patrick Harvie, leader of the Scottish Greens, said: "Today's announcement shows that consistent pressure on ministers from Greens, campaigners, communities and even members of the SNP is working."

Labour's environment spokeswoman Sarah Boyack said:

"For months now the SNP has faced the accusation of being two faced on fracking and unconventional gas by campaigning in elections on anti-fracking platforms whilst reassuring big business behind the scenes that Scotland would be open for business. "They can’t have it both ways but it looks like they're going to try to until at least after the 2016 election."

Scottish Conservative energy spokesman Murdo Fraser said:

"A recent report stated that underground coal had the potential to create a multi-billion pound industry in Scotland, supporting 5,000 jobs.

"It is disappointing that this opportunity is being put on the back-burner as a result of the SNP’s internal difficulties."