A month ago the UK government took the most dangerous decision imaginable in endorsing the MOX plutonium fuel plant at Sellafield.

The global nuclear watchdog body - the Vienna-based International Atomic Energy Agency - finally admitted, after much political pressure worldwide, including in the European Parliament, that nuclear terrorism posed a much bigger threat than it had considered possible.

In the US, overflying nuclear plants has been banned, and the transport of nuclear waste has been halted. Yet the Blair Cabinet in London has virtually invited terrorists world-wide to go nuclear.

The centre of this insanity is Sellafield, from where hundreds of shipments of the deadly nuclear explosive, plutonium, are about to be sent thousands of miles across the high seas.

The tough words against terrorism spoken by the Prime Minister, Tony Blair, are demonstrated to be mere hot air.

How can the British government put the job security of a few hundred jobs of nuclear workers at Sellafield before the security of millions of citizens across the globe?

We are now all in grave danger from radiological sabotage, or an attack on shipments from Sellafield. Ireland, like Belarus next to where Chernobyl is situated in Ukraine, has no nuclear plants, but a terror attack on Sellafield could leave us equally devastated.

According to a European Parliament study released this week into reprocessing and nuclear waste storage at Sellafield, and its French equivalent at La Hague, an accident or an act of malice, such as what happened in New York at the World Trade Centre, if directed at Europe's two plutonium processing plants in the UK and France would have consequences worse than Chernobyl. They are the two EU sites with the largest radioactive inventories.

These plutonium factories are unparalleled worldwide and much more toxic than the average nuclear power plant.

The French government was informed about the consequences for La Hague. It has caused a furore in France, and anti-missile batteries have now been installed to protect the plant from attack.

At our debate in Strasbourg two weeks ago, MEPs asked that the study be passed on to the British government.

A terrorist attack on Sellafield would be devastating to Ireland. The worst scenario would be an assault on Sellafield's dangerous high-level waste tanks.

These are full of volatile radionuclides, such as caesium 137. Recently BNFL closed the Thorp plutonium reprocessing plant because the high-level waste tanks were unable to cope with the current level of waste.

Radioactivity spread from an attack on Sellafield could render large areas of Ireland uninhabitable, and agriculture ruined forever.

We have been warned. According to Dr Edwin Lyman, scientific director of the authoritative Washington DC-based Nuclear Control Institute, in a presentation to NCI's conference, Nuclear Power and the Spread of Nuclear Weapons, held in April this year: "Perhaps the greatest obstacle to a greatly expanded deployment of nuclear power plants, especially to regions of political instability, is the threat that the reactor will become a target of radiological sabotage.

"An armed assault on a nuclear plant's vital safety systems can result in core melt, containment failure and a massive, Chernobyl-like release of radioactive materials into the environment."

The hijacking of passenger jetliners for use as weapons to attack strategic targets is not a threat anticipated in the security analyses of major nuclear facilities.

Concerns include the introduction of plutonium in the form of MOX fuel in a new plant at Sellafield, which is imminently expected to get the goahead from the British government.

MOX may increase the attractiveness of these reactors as targets not only for theft but also for radiological sabotage, because an attack on a MOX-fuelled plant would cause a greater number of casualties.

The UK government should therefore have postponed indefinitely the decision to commission the plutonium-uranium mixed-oxide fuel plant, built by BNFL at Sellafield. If it becomes operational, the plant would be processing tons of plutonium oxide into fresh MOX fuel.

Amounts of plutonium sufficient to induce thousands of latent cancers could be widely dispersed if it were to be attacked.

Belatedly, the Irish Government has now challenged the Sellafield MOX Plant decision at two international forums. In Hamburg, the case in the International Court of the Sea will be formally lodged.

Have British ministers learned nothing from the revelations of BNFL's corporate cheating on MOX fuel data sheets, revealed by the UK Independent newspaper two years ago?

The European Commission should intervene and block any new nuclear plant until a full safety review is completed for all these dangerous plants.

To expand Sellafield's operations in the face of this terrorist threat is simply mad.

Now that the global nuclear agency charged with promoting nuclear energy has conceded the reality of the nuclear terrorist threat, maybe politicians, Ministers and law-makers will start listening to the analysis of the critics who have argued this for years.

Nuala Ahern is a Green Party Member of the European Parliament for the Leinster constituency