The British government is planning an independent scrutiny of the only bid currently on the table for London's Millennium Dome, raising further doubts about the deal going through.

The Irish-backed company Legacy and government officials are struggling to agree final terms before a mid-February deadline. Officials say that even if they do successfully conclude, the bid will have to be examined independently probably by property experts before it proceeds.

Yesterday Treasury Holdings, the Irish property company that owns 80 per cent of Legacy, said it was the victim of a smear campaign after it emerged that MI5 had investigated claims that it had links with the IRA.

The inquiry, begun at the request of the government, found the allegations to be groundless. MI5, which provides counter-terrorism advice to ministers, concluded that claims of an IRA link were based on unsubstantiated rumour.

A Treasury official said the company was as "clean as a whistle". Mr Maurice Harte, Treasury's chief executive, said there had been a "total smear campaign" and "a last ditch attempt by somebody to cause not only us damage, but damage to the project and to the Dome itself".

If the independent analysis proposed suggests the government would raise more by knocking down the Dome or selling it to other bidders for different uses, the Legacy deal would be ditched.

Ministers meet next week to discuss the Legacy offer.

One influential minister said: "We want to make sure the proper process is followed to the absolute letter. If our advisers tell us we'd get better value elsewhere, then so be it."