Protesters against genetically modified crops could find themselves left out of a national debate on the issue.
Six meetings are being held across the UK
All of the 150 tickets available for a public meeting in Glasgow on Wednesday night have been snapped up but many more people are expected to turn up hoping to take part.
Organisers of the event, an independent steering group working on behalf of the government, have added names to a waiting list and said people without tickets may still get into the debate in the Quality Hotel but only if others do not show up.
The meeting is the fifth of six being staged across the UK as part of the GM Nation? debate.
They will be followed by more locally-based meetings during the six-week debating period.
The UK Government, which has contributed £500,000 towards the process, has promised to consider the outcome of the meetings before
making any further policy decisions on the controversial issue.
However, campaigners claim the government is asking the wrong question with its national debate on genetically modified crops.
Friends of the Earth Scotland's chief executive Duncan McLaren said: "The poorly advertised and disorganised GM Nation debate is asking the wrong question.
"The real question is not whether we want corporate controlled GM farming, or business as usual - but how we can best deliver the organic and sustainable food and farming that Scotland's people really want."
Mr McLaren argued that organic farming was the best way forward.
However, he said its future would be put at risk by the commercialisation of GM crops.
He argued: "GM's proponents claim that it will reduce chemical inputs and raise farmers'
incomes, all without significant health and environmental impacts.
"On these criteria organic farming would be better for Scotland - and would also keep control of the food chain out of the hands of the corporate agro-chemical giants.
"The Scottish Executive has a strategy to increase organic production yet if GM is commercialised, organic farming as we know it is probably doomed.
"And there are no rules in place to make the producers of GM crops liable for these and any other costs their products may impose on our environment or health."
Meanwhile, the Scottish Green Party is calling for companies developing genetically modified crops to be made financially liable for any contamination of other crops.
Modification is done either by altering DNA or introducing
genetic material from one organism into another
GM Nation debate organised by an
independent steering board
Due to report its
findings by the end of September
MORI poll in April found 56% of people against GM
products, 14% in favour
It is proposing a bill to establish liability - in the hope it will put companies off getting involved in further GM trials.
"If there's a strict liability that's in place and these companies are liable for any economic losses, then as a result they won't be able to make any money from the sale of the seeds," said Green MSP Mark Ruskell.
Scotland's Rural Development Minister Ross Finnie has urged caution over making decisions about the future of GM crops.
"I think I've made my position absolutely clear, I am wholly opposed to any conclusion being arrived at on this subject before the results of the tests are known," Mr Finnie told BBC Scotland.
"I think that would be wholly wrong, I've made that very clear very publicly and I repeat that."
The man leading the debate, Professor Malcolm Grant, said he hopes the process will reach as wide a section of the public as possible.
But he admits the timing is a difficult issue, with the nationwide debates finishing before the crop trials are completed.
"Because the crop trials have attracted so much public attention I would ideally have liked them to be part of the debate but their publication has been delayed," he said.
"So, we're going ahead with the debate with certain assurances from the government as to the consultation processes they'll try to have when the crop trial results are out in September."
Professor Grant added that the government has pledged to respond to the outcome of the debate in public.