Agencies considering the future use of the Millennium Dome have acknowledged that the site may need to be cleaned up again if more work is to be carried out.

The contaminated soil at the Greenwich site was covered by 18 inches of clean topsoil and a concrete cap. Changing the use of the dome or building other structures on the site could break through to this capped soil.

It also means that the site may not be suitable for residential use unless further remediation is carried out.

Nick Hillard, associate director of consultant WSP, said any further work would have to review the land’s condition.

He said: “Any construction would have to be mindful of what is there. There would have to be a new risk assessment based on its final use. The land’s long-term value to investors could also be affected.”

Alan Micklan, project director at WS Atkins, which carried out the original reclamation work on the site, said: “The land was remediated to a standard acceptable for the Environment Agency and local authority.”

A spokeswoman for English Partnerships, which is considering proposals for the future use of the dome, said each of the bidders was aware of the situation. She refused to comment on suggestions that contamination would make the land too expensive to develop.

“We cannot comment on the value of the site. We are looking at proposals for the site,” she said.

A Greenwich council spokeswoman said the authority believed the site was suitable for most developments.

She said: “It is capable of takconsidering asking for the dome to be made a listed building. She said: “We are in the very ing all the suggested schemes. But it is not suitable for houses with gardens, which we would not support on that site anyway.”

The spokeswoman confirmed that the council is early stages of discussion with English Heritage.”