The Liberal Democrats have backed the lifting of the moratorium preventing fracking for gas in Scotland.

Party members supported an amendment which called for the temporary ban to be ended by the next Scottish government, "providing the potential for Scottish-sourced unconventional gas to supply our important petrochemical industry".

But environmental campaigners at WWF Scotland branded the move "massively disappointing".

Lib Dem activist Ewan Hoyle said expert advice is that unconventional oil and gas extraction - also known as fracking - could be done safely.

In January 2015 the Scottish Government announced a moratorium on granting planning consents for such developments, to allow for a full public consultation on the controversial process.

Mr Hoyle argued that "to maintain a moratorium and ban fracking outright would be to join the SNP in playing political football on the issue".

He said the report from the Independent Expert Scientific Panel on Unconventional Oil and Gas is "really quite reassuring" and "suggests we can extract these unconventional reserves safely if we regulate the industry appropriately".

He told the party conference in Edinburgh: "I joined this party coming from a scientific background, partly because I felt the Liberal Democrats held evidence and expert advice in high regard."

Mr Hoyle also said that with the Ineos petrochemical plant in Grangemouth having built "enormous storage tanks in order to accept imported fuel from the US", he believes it would be "more environmentally friendly to manufacture our own petrochemicals and drive a resurgence in Scottish manufacturing from locally sources methane".

He said: "I would far rather support Scottish jobs and reduce the environmental impact of transport by burning Scottish gas."

His amendment replaced part of the original motion, which had supported continuing the moratorium to allow for a "full assessment of the risks involved and the long-term implications" of fracking.

WWF Scotland director Lang Banks said: "The climate science is very clear that we need to start leaving fossil fuels, including unconventional gas, in the ground. It's therefore massively disappointing to see what would have been a very strong Lib Dem position on tackling climate change undermined by the inclusion of support for fracking.

"There is overwhelming public opinion in favour of cleaner forms of energy and a sufficient body of evidence why unconventional oil and gas are neither good for people or the planet. It's just one of the reasons why, as we approach the Holyrood elections, we want each of the political parties to commit to ensuring Scotland becomes the EU's first fully renewable electricity nation by 2030."

Scottish Green Party co-convener Patrick Harvie said: "Just days ago Willie Rennie told an audience in Glasgow that his party would try to ban fracking even though they agreed to back fracking at their conference three years ago; now he'll have to campaign for the moratorium to be lifted.

"Scotland can ban fracking and coal gasification now with the powers we have and only the Scottish Greens have consistently called for a permanent ban to protect our communities and our climate.

"With the Scottish Government failing to rule it out, and Labour continuing to sit on the fence, it is clear that more Green voices are needed at Holyrood to kill off this dangerous distraction so Scotland can invest in sustainable industries to create the jobs of the future."

Scottish Liberal Democrat leader Willie Rennie said the party had "basically decided to go on the scientific evidence about the safety issues, allowing local authorities to decide whether they want to go ahead with fracking".

He added: "It fits in with our localism credentials and also basing it on science, because I think the reports are pretty clear now in terms of safety, it's not really an issue."

Mr Rennie stressed: "I want to accelerate a move towards renewables and carbon-free fuels, I think that's the right direction to go. But the party has decided, because we're very keen on science, that local authorities should be able to decide for themselves whether to go ahead or not."