Greenpeace has accused the Government of failing to do enough to prevent a shipment of weapons grade plutonium which is believed to have passed within 150 miles of the Irish coast in recent days.
The shipment, which is taking 140 kilogrammes of surplus plutonium oxide from the United States' nuclear weapons programme for reprocessing into nuclear fuel in France, is expected to dock at Cherbourg in the next few days.
The criticism came as anti-nuclear activists were arrested yesterday after they entered a military exclusion zone near the military facilities at Cherbourg port. The activists were part of a Greenpeace-organised flotilla, which was awaiting the arrival of the armed nuclear convoy.
The convoy consists of two British-registered ships, which are owned by British Nuclear Fuels Ltd (BNFL), the operators of the Sellafield plant. The ships were loaded with the material at Charleston, South Carolina, last month.
BNFL was refusing to divulge the current location of the convoy or when it was due to dock in Cherbourg. This was a standard security precaution regarding nuclear shipments, according to a spokeswoman.
Yesterday a spokesman for the Department of the Environment defended the Government's actions, stating that it had sought and received assurances that the ships would not be entering Irish waters.
This was the most that the Government could have done, as the ships were entitled to free passage, the spokeman added.
Senior figures in Greenpeace yesterday criticised what they said was a lack of action on the shipment by the Government, which has a stated position against nuclear energy.
There were also unconfirmed reports that an Air Corps spotter plane was used to ensure the ships remained outside Irish waters.
In a letter three weeks ago, Greenpeace urged the Government to complain to the European Commission in order to halt the shipment.
The environmental lobby group argued that Ireland could make an intervention regarding the issues of safety because of the record of the nuclear fuel plant, Caderache in Provence, which is due to reprocess the weapons material.
There have been concerns over its safety record, including the latest alert last month, after a number of workers were contaminated with small doses of nuclear radiation.
Yesterday Mr Shaun Burnie, nuclear campaigns director with Greenpeace, said that the Government had not responded to its letter.
"We've had no official response," Mr Burnie said. "I have to say it's a bit pathetic."