The Independent newspaper reported that the document showed at least six separate items on Saddam's alleged weapons of mass destruction were lifted from reports up to 21 months old.

Downing Street has acknowledged that it made a mistake in failing to credit work by an American student used in its February dossier, but has stoutly defended the integrity of the September document.

But The Independent claimed that the earlier dossier drew heavily on sources already in the public domain.

They were a briefing paper by William Cohen, US Defence Secretary in the Clinton administration, from January 2001; the appearance before the Senate select committee on intelligence by CIA director George Tenet the following month; an unclassified CIA report to Congress covering the period July 1 to December 31, 2000; and a report on Iraq by the International Institute for Strategic Studies published in London last September.

These pieces of evidence included references to ballistic missiles; unmanned drones; nuclear programmes; "dual use" of civil materials; maps showing how British bases in Cyprus were within range of Iraqi missiles; and Saddam's supposed plan for regional domination.

A Downing Street spokesman noted that during his appearance before the Commons foreign affairs select committee earlier this week Prime Minister Tony Blair stood by the intelligence material presented to the public.

"We have said all we have to say on this," the spokesman said.

There is considerable doubt in London and Washington over the strength of the US and British case for ending UN arms inspections and launching the March 20 invasion to topple the Iraqi leader Saddam Hussein.

WAR.WIRE