Peter Mandelson, the local MP, accused the groups of "colossal misinformation" after personally inspecting the two ships that docked in the north-eastern port last week. And senior government sources pointed out that the ships - continually described as "toxic timebombs" by environmentalists - are in fact "no more toxic than the average car ferry".

On Wednesday, Elliott Morley, the Environment minister, and top officials from the Environment Agency will aim to straighten the record at an emergency hearing to be held by the House of Commons Environment, Food and Rural Affairs Committee.

Sensing that the environmentalists have overplayed their hand, the Government yesterday abandoned its attempts to persuade the US to make the two ships at sea turn back, and suggested that all four might be dismantled in Hartlepool and not returned to the US, as it had previously insisted.

Friends of the Earth said it was disappointed and called on the Government to "keep its promise" and "stand up for the people of Teesside" by eventually sending all four back across the Atlantic. But scrutiny is increasingly focusing on the group and Greenpeace, which must both explain why they have told the public the ships pose an exceptionally serious threat, when they actually contain less-dangerous materials than many hundreds of vessels uncontroversially plying the seas. Friends of the Earth has claimed that bringing them to Teesside is "extremely hazardous", while Greenpeace described them as carrying "cocktails of hazardous substances."

As a result, nine out of every 10 people in Hartlepool - who stood to gain 200 jobs from the work - told a local poll they did not want the ships: the town council unanimously expressed the same view.

But a glance at what is actually in the two ships now in Hartlepool - the Canisteo and the Caloosahatchee - shows how unnecessarily they have been frightened. The nastiest stuff on board is asbestos, 55 tons on each vessel. It is indeed deadly, but only if the fibres break loose and are inhaled. In fact the mineral is built into the structure of the vessel and pipework as insulation, just as in hundreds of other ships - and in schools and hospitals throughout Britain.

Next come polychlorinated biphenyls (PCBs). These are hazardous chemicals, suspected of causing cancer and "gender-bender effects", but are only present on the ships in solid form in such everyday products as insulation around electrical cables, glass fibre and paint. Even Friends of the Earth admits that the risk of them leaking out is "negligible".

The only pollutant on board that could leak and cause trouble is oil - but there are only tiny amounts. The Canisteo contains about 34 tons; the Caloosahatchee just one and a half.

The inventories of the next two ships - the Compass Island and the Canopus - are similar, though each contains 273 tons of asbestos and a couple of hundred tons of oil.

The full fleet of 13 ships eventually due to come to Hartlepool are carrying just 3,500 tons of oil between them - a fraction of the amount carried on a single oil tanker.

The only clear hazards are to workers if the material is stripped out carelessly, and to the environment if they are dumped irresponsibly. But the Environment Agency says the Hartlepool yard is "as good as any in the country" and even Greenpeace admits conditions there "are far more advanced" than those under which most ships are scrapped.

The scaremongering has, however, obscured some valid concerns. Able UK did not have all the necessary planning permissions and had not adequately investigated the possible effects of its work on the environment.

But the important thing is that the ships are scrapped safely: the Government says the Hartlepool yard was chosen because it was better than the alternative facilities available in the US. And the vital consideration is that they are not sent to join the hundreds being scrapped without any precautions in the Third World.

The real dangers are that the storm created by the pressure groups will ensure future ships avoid Britain and get dismantled in India - and that, by crying wolf, the environmentalists will have less influence in debates on GM crops or global warming.