THE SNP leadership is facing demands from within its own ranks to spell out exactly what is covered by its controversial moratorium on fracking amid opposition claims that ministers are deliberately misleading the public.

Nationalist parliamentarians in both Westminster and Holyrood have called for clarity as ministers continue to dodge questions over their policy six months after the moratorium was called.

Ministers are also facing calls from their own backbenches to toughen their stance on all unconventional oil and gas developments by extending the temporary ban to plans to ignite coal under the Firth of Forth.

Ineos, the firm that wants to establish a large-scale fracking industry in Scotland, plans to begin test drilling within 12 to 18 months while Cluff Natural Resources, which wants to exploit coal under the Firth of Forth through a controversial process known as underground coal gasification (UCG), is set to submit a planning application early in 2016. Both companies have been in private dialogue with SNP ministers.

John McNally, the MP for Falkirk which would likely be a fracking hot-spot should it get the go-ahead, said his SNP colleagues at Westminster viewed unconventional oil and gas with "trepidation" and called for clarity over what is covered by the moratorium.

Mr McNally, the SNP group convenor on fracking at Westminster, said: "My understanding is that the moratorium banned all drilling until we had all the evidence. I think that’s the position we should be maintaining."

Asked whether UCG should be included in the moratorium, he said his position was "quite simple and straightforward", adding: "At the moment it should be included."

Angus MacDonald, the SNP MSP for Falkirk East, has asked the Government whether test drilling is covered. He said he hoped to receive a response before Holyrood reconvenes at the end of next month, but that if one was not forthcoming, energy minister Fergus Ewing should make a statement to parliament to spell out exactly what the moratorium means.

He added: "There’s also underground coal gasification, which is an issue we need clarification on. As long as there are unanswered questions, there shouldn’t be any work. There are concerns with pollution to groundwater which are valid in my book."

A series of other written questions at Holyrood submitted as far back as February seeking further details have yet to receive substantive answers, which are usually issued within around three weeks.

John Wilson, the MSP who quit the SNP last September, submitted questions in March and despite being told in April he would get a reply from Mr Ewing "as soon as possible", is still waiting.

Mr Wilson, who sits as an independent but will stand as a Green candidate next year, said: "I find the Scottish Government is being disingenuous. It would be useful if they came clean sooner rather than later on whether they intend to allow fracking and UCG.

"It would be interesting to find out if the First Minister and Energy Minister have been pulling the wool over the eyes of not only the electorate but a large number of party members during the Westminster campaign who wore anti-fracking badges with the SNP logo on them.

"Anybody critical of the SNP faces a barrage of accusations of undermining the SNP and the Scottish Government... of scaremongering. But the reality is the SNP government has got to be held to account like any other."

During the general election campaign, the SNP adopted the 'Frack Off' slogan and presented itself as anti-fracking with many members and parliamentarians strongly opposed. In his maiden speech at Westminster, Martyn Day, the MP for Linlithgow and East Falkirk said of fracking "I just dinnae like it" and vowed to oppose any applications.

Fracking, which sees wells drilled deep into the earth before water, sand and chemicals are pumped in to release gas trapped in shale rock, could prove potentially lucrative for the Scottish economy and deputy First Minister John Swinney has already called for taxes it might generate to be assigned to Holyrood.

Ineos chief Jim Ratcliffe, who met privately with Nicola Sturgeon on the day the moratorium was announced, has said he received private assurances from the SNP Government that it was "not against" the technique. The firm, which has embarked on a PR drive to win over public opinion, does not plan to frack for at least three years and is yet to be directly affected by the moratorium.

The moratorium, announced on January 28, came days after Labour put pressure on the SNP by saying local referendums should be held before fracking developments got the go-ahead, even if the technique was shown to be safe. Lewis Macdonald, the party’s energy spokesman, has said that he doubts the policy has had any impact whatsoever on firms pursuing unconventional oil and gas developments and that he believes ministers are secretly keen to give the green light to raise tax revenues.

A Scottish Government spokesman said: “Exploration licencing for onshore unconventional oil and gas is being devolved but the licensing for underground coal gasification is not being devolved. UCG exploits coal reserves and is licenced by the Coal Authority.

“The Scottish Government is clear that the development of new energy technologies, such as underground coal gasification, must be consistent with our environmental objectives and we will continue to take a careful, evidence-based approach to such developments.”