NICOLA Sturgeon is facing fresh pressure over a proposed ban on GM crops after the government refused to say whether its own chief scientific adviser for rural affairs was consulted on the move.

Rural Affairs Secretary Richard Lochhead announced the ban last month, saying it would ensure Scottish produce continued to be seen as a "clean and green brand" around the world.

However the decision was criticised by leading scientists, who warned it would undermine the country's contribution to the research and development of genetically modified crops.

Around 30 organisations, including some of the country's most important research institutions, claimed in an open letter to Mr Lochhead the decision was "political and not based on any informed scientific assessment of risk".

Murdo Fraser, the Scottish Conservative MSP yesterday called on the First Minister to say whether Professor Louise Heathwaite, the chief scientific adviser to Mr Lochhead's rural affairs and environment department had been consulted.

In a letter, he said her views should be made public and "specifically whether she gave an opinion on the matter prior to the announcement".

The Scottish Government has repeatedly declined to say whether Professor Heathwaite was consulted on the decision.

Challenged about the basis for the ban during First Minister's Questions on Thursday, Ms Sturgeon told MSPs: "We have a chief scientific adviser for rural affairs, food and the environment in post" but, when pressed, failed to confirm whether her advice had been sought.

Later, a Scottish government spokesman said Professor Heathwaite was "a source of expert advice on a range of issues".

It emerged last month that ministers did not have the option of consulting the government's overall Chief Scientific Adviser as the post has lain vacant since last year.

Mr Fraser said: "What is the point of the Scottish Government employing scientific advisers if it then doesn't consult with them?

"If you are making a significant policy announcement which should have a significant scientific input, it really calls into questions this government's to science and listening to the views of scientific experts."

Mr Lochhead said last month Scotland would seek to be excluded from any European consents for the cultivation of GM crops, a plan since adopted by Germany.

The move came as a surprise but he said he was not prepared to "gamble" with the future of the country's £14billion food and drink sector.

He said producers feared a "consumer backlash".

Ms Sturgeon repeated the case when she was asked at Holyrood about the concerns raised by leading research institutes.

Asked specifically if Professor Heathwaite was consulted, she told MSPs: "I have outlined the rationale and basis for the Scottish Government’s decision.

"I will defend the decision, because I think that it is right for a sector that is hugely important to our economy."

Professor Heathwaite, who is based at Lancaster University, failed to respond to calls and emails from The Herald.

A Scottish Government spokeswoman said: "The Scottish Government made this decision on the basis that we are not willing to risk Scotland’s multi-billion food and drink sector. Like Europe's biggest country, Germany, we have restated the long-held policy to maintain a precautionary approach to GM.

"GM crops go through scientific assessment before going onto the EU's authorised list but Scotland is taking advantage of the EU's decision to allow member states and parts of member states to opt out for non-scientific reasons.

"Both SASA (the Scottish Government agency Science and Advice for Scottish Agriculture) and the Chief Scientific Advisor for Rural Affairs, Food and the Environment are sources of expert advice on a range of issues that help inform the Government's position."