Scottish National Party environment spokeswoman Fiona McLeod called on the Lib Dems to follow the line agreed at their party conference last month.

A motion on GM crops, published by Ms McLeod, is to be debated in the Scottish Parliament in Aberdeen on Wednesday.

Ms McLeod is also expected to produce evidence that she believes will support the SNP's call for an immediate ban on trials of GM crops.

Ross Finnie said the trials should continue

Twelve trials of GM oilseed rape have taken place in Scotland and the final planting of GM seeds is scheduled to take place next year.

Last month, delegates at the Scottish Liberal Democrat conference in Perth supported an amendment calling for an immediate moratorium on field testing and commercial growing of GM crops in Scotland.

Scotland's Rural Development Minister Ross Finnie, a Liberal Democrat MSP, told the conference that he had to accept European laws on the issue and allow the trials to continue

Mr Finnie said there is no scientific evidence to support such a moratorium.

Ms McLeod's motion calls for "the precautionary principle" to be used, halting the field scale trials and restricting future testing to enclosed laboratories.

Scientific evidence

Ms McLeod said: "Our motion calls on the Liberal Democrats to stand by their principles and follow the line agreed at their party conference last month which called for a moratorium on GM crops.

"Mr Finnie claims there is no scientific evidence to support such a moratorium, but we have new research which we will reveal tomorrow which proves our case and backs up the need for an immediate ban on GM crop field trials."

Anti-GM campaigners opposed to trials taking place at Munlochy on the Black Isle urged MSPs "to vote with their convictions and listen to their constituents".

One of the campaigners, Anthony Jackson, said: "This is especially so for the Highland MSPs who have signed the petition, including Maureen Macmillan, Rhoda Grant and Jamie Stone.

"We are sure that constituents in other areas where GM trials are being carried out will also watch closely to see how their MSPs vote."