PRESSURE was growing on the US last night to halt obsolete navy ships heading to a North-East yard after the British Government said they should return home.

Environment Minister Elliott Morley said the four rusting hulks - condemned by environmentalists as a toxic hazard - must go back until a planning wrangle is sorted out.

And he revealed that the Environment Agency had urged US officials not to allow the ships to sail three days before they put to sea.

Mr Morley also held out the possibility that the ships might be sent to a foreign country for dismantling if planning permission is not granted for work to be carried out at Able UK's yard in Hartlepool.

But last night the US authorities said the ships would sail on.

Four of the 13 vessels contracted for disposal in the UK are being towed across the Atlantic by tugs.

Two are north-west of the Azores, having refuelled at sea, the others are about a quarter of the way across.

Environmentalists fear the ships may soon be unable to return home because the risk of towing them back to the US in bad weather will be too great.

Until now, the Government has been keen to keep out of the argument over whether the £11m contract should go ahead.

But during an emergency Commons debate yesterday, Mr Morley said: "The Government's position is clear - that these ships should turn back.

"The advice by the Environment Agency, and given very clearly to the US authorities, is that the ships should return or another environmentally sound solution should be found.

"That might be, for the sake of argument, a yard that meets the standard in another country, if one exists."

The deal to tow 13 US ships to Hartlepool for recycling was originally approved by the Environment Agency but then blocked last week.

The organisation withdrew its approval for Able UK's contract with US authorities to dismantle 13 vessels contaminated with chemicals, including polychlorinated biph-enyls, asbestos and heavy diesel.

The agency said it was concerned that planning and environmental requirements for the dry dock dismantling had not been met.

Mr Morley said: "These ships will not be allowed to enter UK waters if they are in an unseaworthy condition.

"However, the proper planning consents are not in place. Until they are, the Environment Agency's advice is that they should return to the United States."

The Americans have said they received official approval from the agency before the first ships departed, and said the vessels would never have left their moorings without it.

But Mr Morley told the Commons: "The agency did act on the doubts that were emerging and advised that the ships should not leave until they were resolved.

"When it became clear there might not be all the correct consents in place, the Environment Agency contacted the US authorities on October 3 - before the ships sailed. Its advice was the ships should not leave the US. The first ships sailed on October 6."

Mr Morley promised a "full evaluation of why there has been these problems and what lessons we can learn".

A spokeswoman for the US Maritime Administration (Marad) said last night there had been no change of heart.

But she added: "We are aware of the new position and will continue to work with all the agencies involved.

"Marad is taking a very much wait-and-see approach at the minute. We don't have all the facts so it is difficult to say what we will do next."

Able UK remained defiant, saying it did have the relevant permissions to begin the operation.

A spokesman said: "We were not aware that the issue was to be raised in the House of Commons this afternoon and, therefore, we have not had an opportunity to study the comments made.

"Once we have had a chance to examine what was said by the minister and other MPs we will be in a position to respond.

"We remain satisfied that we have in place the relevant permissions relating to the movement and recycling of the vessels and the provision of the appropriate conditions for carrying out the work at our TERRC (Teesside Environmental Reclamation and Recycling Centre) facility.

"As Marad have made clear, the vessels are continuing their journeys while we work to resolve the issues."

Environmental group Friends of the Earth urged the Government to get tough and order the ships back.

Director Tony Juniper said: "The US government is ignoring calls from the Environment Agency for these Ghost Fleet ships to be returned to the United States.

"Perhaps they would listen if Environment Minister Elliot Morley made it clear that these toxic hulks will not be allowed to enter UK waters."