The veracity of the government's case for war against Iraq is again under scrutiny.

Renewed controversy came after the Hutton inquiry published an email from the prime minister's chief of staff which revealed splits over the evidence against Saddam Hussein.

The email, written by Jonathan Powell, warned against using the dossier to convey the impression that Iraq posed an "imminent" threat to the UK.

Written to intelligence chief John Scarlett, and copied to Sir David Manning and Alastair Campbell, the email reveals unease at the way the government was attempting to build its case for war.

"The document does nothing to demonstrate a threat, let alone an imminent threat from Saddam," said Powell.

"In other words it shows he has the means but it does not demonstrate that he has the motive to attack his neighbours let alone the west."

Powell added that "we will need to make it clear in launching the document that we do not claim that we have the evidence that he is an imminent threat".

Yet less than a week later the prime minister insisted that Saddam Hussein could mobilise weapons of mass destruction in just 45 minutes.

The shadow foreign secretary, Michael Ancram, called on the government to clear up the growing confusion.

"A week after Jonathan Powell said that there was no threat or it did not pose a threat let alone an imminent threat the prime minister... was talking about a serious and current threat to the interests of the United Kingdom," he said on Monday night.

"It does explain possibly why the 45 minute deployment in that dossier was given such prominence.

"There was obviously a feeling that it did not give the impression of sufficient threat for the purposes of the government at that time and that there was a hyping up of it."