An alliance of community and environmental groups has called for the Scottish Government's moratorium on fracking to be extended to cover underground coal gasification.
Almost 30 organisations and individuals, including residents' associations, academics, Friends of the Earth and Unison Scotland, have made the plea in a letter to energy minister Fergus Ewing.
Campaigners welcomed the moratorium on unconventional oil and gas developments announced by Mr Ewing last month but say it does not go far enough.
The letter to Mr Ewing says they are "gravely concerned" that underground coal gasification, a technique which produces gas from coal seams underground, is not included in its scope.
Energy company Cluff Natural Resources is drawing up plans to extract coal from under the Firth of Forth.
The company says a study has found as much as 335 million tonnes of coal near Kincardine and is now seeking permission to build the UK's first deep offshore underground coal gasification project to extract it.
The letter said: "Many of the environmental and public health impacts of underground coal gasification are understood to be very similar to those of shale gas and coalbed methane extraction.
"While we are disappointed that Coal Authority licensing is not proposed to be devolved to Holyrood under the Smith Commission, we note that the means of imposing a moratorium on unconventional oil and gas developments - ensuring that no planning permissions or environmental permits are granted for these developments - could equally be applied to underground coal gasification, therefore we strongly urge you to extend the scope of the moratorium and related work to this experimental technology."
Mary Church, Friends of the Earth Scotland head of campaigns, said: "Underground coal gasification is the most experimental and frightening method of unconventional gas extraction currently threatening Scottish communities.
"Not only have recent trials around the world gone badly wrong, but the likely climate impact of this inefficient technology is simply unacceptable.
"It makes no sense for a country with ambitious climate targets and the means to achieve them with renewables to flirt with such a risky form of energy production.
"Communities threatened with Cluff's plans to ignite the coal under the Forth are asking why hasn't the Scottish Government acted to protect them in the way that communities facing shale gas fracking and coal bed methane drilling are.
"The case to include underground coal gasification in the new moratorium and planned work on health and environmental impacts of unconventional gas is crystal clear, and the means of doing so totally within the power of the Scottish Government."
The fracking moratorium has been proposed while a full public consultation is carried out, alongside further research into the technique to look at planning, environmental regulation and the impact on public health.
A Scottish Government spokesman said: "The Scottish Government continues to take a careful, considered and evidence-based approach to unconventional oil and gas and fracking - an approach now underpinned by the recent moratorium announcement, which outlined our plans for a full public consultation and further research.
"The moratorium is specifically about onshore unconventional oil and gas developments, including fracking - further to confirmation by the UK Government that it would devolve onshore licensing powers for these types of development.
"Many of the relevant powers relating to underground coal gasification remain with Westminster and the licensing regime is not being devolved, though we will work with Sepa and all relevant regulators to ensure we have the appropriate controls and regulations to protect the environment.
"The Scottish Government will continue to take an evidence-based approach to the development of new energy technologies, which should give security and confidence to the people of Scotland that such resources would be developed in an environmentally safe and satisfactory way."
Why are you making commenting on The Herald only available to subscribers?
It should have been a safe space for informed debate, somewhere for readers to discuss issues around the biggest stories of the day, but all too often the below the line comments on most websites have become bogged down by off-topic discussions and abuse.
heraldscotland.com is tackling this problem by allowing only subscribers to comment.
We are doing this to improve the experience for our loyal readers and we believe it will reduce the ability of trolls and troublemakers, who occasionally find their way onto our site, to abuse our journalists and readers. We also hope it will help the comments section fulfil its promise as a part of Scotland's conversation with itself.
We are lucky at The Herald. We are read by an informed, educated readership who can add their knowledge and insights to our stories.
That is invaluable.
We are making the subscriber-only change to support our valued readers, who tell us they don't want the site cluttered up with irrelevant comments, untruths and abuse.
In the past, the journalist’s job was to collect and distribute information to the audience. Technology means that readers can shape a discussion. We look forward to hearing from you on heraldscotland.com
Comments & Moderation
Readers’ comments: You are personally liable for the content of any comments you upload to this website, so please act responsibly. We do not pre-moderate or monitor readers’ comments appearing on our websites, but we do post-moderate in response to complaints we receive or otherwise when a potential problem comes to our attention. You can make a complaint by using the ‘report this post’ link . We may then apply our discretion under the user terms to amend or delete comments.
Post moderation is undertaken full-time 9am-6pm on weekdays, and on a part-time basis outwith those hours.
Read the rules hereComments are closed on this article