SNP ministers are under mounting pressure to explain why a controversial process for burning coal under the sea bed is not included in a moratorium on unconventional oil and gas developments.

The Herald revealed Friday that Cluff Natural Resources, the firm that wants to convert coal reserves under the Firth of Forth to gas under a process known as underground coal gasification (UCG), will submit a planning application within months.

Advocates insist the process can be carried out safely, although environmentalists have pointed to a project in Australia which was shut down within days after groundwater was contaminated.

The Scottish Government initially indicated that it had no powers over UCG, as it was technically offshore. However, it has since admitted this is not the case, as essential onshore infrastructure would require planning permission which is controlled by Holyrood.

But ministers have refused to extend a moratorium on unconventional oil and gas developments to UCG, and six months on, is yet to explain what is covered by the temporary ban and when new research or a public consultation will be carried out.

Lesley Laird, the Labour deputy leader at Fife Council, which is one of the areas in which Cluff may submit its planning application, said the Scottish Government may also be able to block the development as permission for offshore activity would have to be granted by Marine Scotland.

"This lack of clarity and transparency is simply not good enough," Ms Laird, also spokesperson for economy and planning at the authority, said. "The Scottish Government have had repeated requests to bring UCG into the scope of the moratorium and they have simply been trying to avoid doing so. Why?"

She added that the statements from Cluff Natural Resources and Jim Ratcliffe, the boss of chemical giant Ineos which wants to establish a fracking industry in Scotland, were cause for "considerable concern" in Fife.

"What is even more concerning is that as a local authority who could potentially be affected by these plans we have not been consulted or contacted for our views," she said. "It is still not evident what this consultation will look like and the longer this rumbles on then quite rightly the more concerned people should be.

"The Scottish Government needs to be clear and honest about their intentions on this issue. Are they going to include UCG in the moratorium or not? It's a simple question. If there is not a "yes" response to this then it clearly begs the question of what have Scottish Government officials agreed with Ineos and Algy Cluff?

"As a matter of urgency I will once again be raising these questions with Scottish Government ministers. People in Fife and Scotland need to know once and for all - is the Scottish Government now going to include UCG in the moratorium and when will Fife and Scotland be consulted?"

The Scottish Government said that any new energy technologies would have to be consistent with its environmental objectives, and that it would take an "evidence based approach".

A spokeswoman added that licensing for onshore developments was being devolved, but that this would not be the case for UCG which will remain under the control of the Coal Authority.

Alison Johnstone, the Green MSP, said the claim from Cluff that its planning application would go through "smoothly" showed that the firm was "out of touch" with communities.

She added: "Chasing after yet more dirty energy goes against our climate change duties and poses too many risks for communities. Scottish ministers have the power to end this uncertainty."