Campaigners have called for checks on land around all nuclear power stations after the full extent of contamination at an Ayrshire site came to light.
BNFL has reassured those living near the plant
An estimated 81,000 cubic metres of soil at Hunterston A are affected.
The site's owner said the radiation dated back to the 1970s and that levels were well within safety limits.
Friends of the Earth said people needed to be reassured - but former energy minister Brian Wilson dismissed the fears as "scare stories".
The Labour MP for Cunninghame North said that those who had voiced concerns were the "usual bunch of anti-nuclear activists who rely on scare stories to prop up their cause".
And he said: "This is a very familiar story to anyone who knows the history of the Hunterston A site.
"Decontamination of the site is an integral part of the decommissioning process and will continue to be so over a very long period."
But Scottish Green MSP Shiona Baird, the party's co-convener, said: "What scares me most is Brian Wilson's dismissal of it as a scare story. That to me is really frightening."
British Nuclear Fuels (BNFL) owns the site, which ceased operating in 1990.
It said that the contamination dated back to the 1970s.
Radioactive material leaked from cracked effluent pipes and from open-air cooling ponds, which were covered over when the problem came to light.
The company added that the levels of caesium-137 which had been found were 100 times below the accepted limits.
Work is being carried out to come up with a preferred strategy for disposing of the radioactive material.
Site manager Jim Craik offered reassurance to those living near the plant.
"We have an area of contaminated land which is quite substantial - much more substantial than we would like," he told BBC Scotland's Politics Show.
"But this land was contaminated in the 1970s, it is not something new.
Duncan McLaren said nuclear power was unsafe
"During the 1970s when it was identified, it was brought to the attention of the regulators and they were satisfied that the actions we were taking were
He said BNFL was trying to manage the land to ensure that the material did not spread outside the site boundaries.
And he added: "We don't know how much land is affected.
"We have done a survey of the surface of the ground which tells us the area that is affected, but we do not yet know in detail the depth to which this contamination has penetrated."
However, Ms Baird said: "We do not know what is a safe level of radiation.
"We don't know how much we are being influenced by radiation from other sources that have not been declared and I think it is this that we really need to concentrate on," she said.
Friends of the Earth said contamination checks should be carried out on land around all nuclear power stations.
Chief executive Duncan McLaren said people living and working in and around nuclear facilities had to be reassured.
"Despite decades of support and billions of pounds in public subsidy, nuclear power remains an uneconomic, unsafe and unwanted energy technology," he said.
"Those who think new nuclear power plants should be built should think again."