Permission has been secretly granted for the derelict vessels to be towed 4,000 miles to Teesside, where they and their contents will be broken up and buried. They hold hundreds of tonnes of asbestos and some of the most poisonous chemicals known to man. It promises to be a fraught voyage: the convoy of 13 vessels must risk ferocious Atlantic storms, and also the world's busiest shipping zone - the English Channel.

The Observer can reveal that the controversial deal will be signed tomorrow, having obtained government approval on Friday. Next month, the ships will leave their base in Virginia, where they have lain corroding and disused for decades amid repeated pollution scandals.

Another 80 derelict ships - condemned as 'toxic floating dumps' by some - may follow the route to North East England, where they will be torn apart at shipbreaking yards. Their 11,000-tonne hulks will be buried in landfill sites near Hartlepool.

The deal has been shrouded with secrecy. Yet an investigation into why Britain accepted the contaminated US warships has raised fresh doubts over it. The agreement appears to contravene international regulations on transporting dangerous goods. It has also emerged that the US authorities even offered 'sweeteners'.

Following frantic negotiations last week, the Govern ment sanctioned the deal. The Health and Safety Executive has lifted an order banning the import of asbestos, which has claimed hundreds of lives in shipyard communities.

Campaigners claim the deal makes Britain a dumping ground for US poisons. The age of the vessels is a further cause of concern: many of the warships and tankers date back to World War II. Some hulls may be so corroded that a hammer could penetrate them. US transport officials have called the vessels 'ticking timebombs'.

News of their imminent arrival has stunned Teesside residents. One campaigner, Peter Goodwin, said: 'We have grave concerns about the risks to coastal waters and to the river. We fear a long-term commitment to dealing with hazardous wastes will reinforce the area's unfortunate image as an international toxic dump.'

Sources close to the multi-million-pound deal indicate the Government backed it on the grounds it would create 200 jobs. The deal has been secured by shipbreakers Able UK, operating the Hartlepool landfill site and a dry dock at nearby Graythorp.

However, safety worries were heightened when a blaze erupted at the landfill site last week. Eight fire appliances worked for hours tackling a blaze involving 40 tonnes of 'low hazardous' waste.

The amount of toxic polychlorinated biphenyls (PCBs) - banned in the 1970s and linked to cancers in humans - within the fleet is unclear, although the most volatile compounds will be removed before setting sail. Each ship holds an average of 98 tonnes of asbestos. A spokesman for the HSE admitted that, while allowing asbestos to be imported, it was sensitive to the fact the toxic fibre had created misery in regions such as Teesside.

Five years ago, US President Bill Clinton ruled that the ghost fleet could not be scrapped in Third World countries after toxic loads of similar vessels had lead to the deaths of workers.

However, President George Bush persuaded the US Environmental Protection Agency to lift the ban for this contract. It has emerged that the US authorities offered a 'sweetener' to Able UK in the form of two new 'oiler' vessels that can be sold on - an incentive not available to US companies.

Able UK managing director Peter Stephenson said it had worked on such contracts safely for 16 years. Only vessels fully shipshape would be towed to Britain, he added.