Parliament's intelligence and security committee has concluded that there was "convincing intelligence" that Iraq had active chemical, biological and nuclear programmes and the capability to produce chemical and biological weapons.

But it warns that a lack of consensus about what constitutes a weapon of mass destruction is leading to widespread public confusion about the threat posed by Iraq.

The committee's report said that WMD could result in thousand of casualties if deployed against civilians.

"However, the same term is used to cover battlefield or tactical munitions including artillery shells with a chemical payload, such as mustard gas, for use against opposing troops," added the report.

The threat posed by Iraq as a result of its failure to comply with United Nations resolutions on WMD was a key issue in the run up to the war.

But with no such weapons yet uncovered by coalition experts, the credibility of the intelligence agencies has faced unprecedented scrutiny.

The committee report sets out three assessments on Iraq which had been approved by the Joint Intelligence Committee (JIC).

At the time of the first Gulf war it was believed that Iraq had chemical and biological weapons and ballistic missiles in a state where they were ready for deployment.

While it lacked a nuclear capability it was "trying hard" to develop one, the committee noted.

From the end of the first war to 1998 Iraq failed to cooperate with United Nations weapons inspectors and was thought to have retained some chemical and biological agents, as well as some missiles.

And from 1999 to September 2002 the JIC believed that Iraq continued with a "programme of concealment and deception to hide its WMD work".

Crucially, the intelligence community was also advising the prime minister that Iraq had a chemical and biological weapons capability and was able to produce ballistic missiles.

This later analysis was based on intercepted Iraqi communications as well as "human intelligence" on the ground.

There have been two key concerns arising from the first intelligence dossier on Iraqi capabilities.

These have related to the claim that WMD could be launched "within 45 minutes" of an order from Saddam Hussein, and the accusation that Iraq sought to acquire uranium from Africa.

Debate over these issues has become particularly heated in the months since the BBC's Andrew Gilligan reported that the 45 minute claim had been inserted in the knowledge that it was probably wrong.

It has also been suggested that the uranium purchase claim was based on a forged document rather than accurate intelligence.

Despite the doubts of some, the MPs and peers on the committee appear to have been convinced that intelligence genuinely showed Iraqi WMD posed a threat.

"Based on the intelligence and the JIC assessments that we have seen, we accept that there was convincing intelligence that Iraq had active chemical, biological and nuclear programmes and the capability to produce chemical and biological weapons," said the report.

However, while the September dossier was a "balanced assessment" it failed to highlight the "uncertainties and gaps in the UK's knowledge" of Iraqi WMD.

It has already been confirmed that the 45 minute claim contained in the September dossier was based on intelligence from a single source.

Much of the criticism of this claim appears to have arisen because some intelligence analysts believed there was a lack of evidence to support such a claim.

One such expert was Dr David Kelly, while two members of the Defence Intelligence Staff also wrote to their line manages expressing doubts.

However, with the publication of the report it has been confirmed that the intelligence that prompted the 45 minute claim was made available only to senior intelligence officials.

Therefore many of those who questioned the claim would have been unaware of the intelligence that it was based upon.

The committee also revealed that the 45 minute estimate set out in the dossier had been a conservative analysis.

It was thought by the JIC that Iraq's chemical or biological weapons could be used "within 20 to 45 minutes".

An assessment concluded: "Intelligence also indicates that chemical and biological munitions could be with military units and ready for firing within 20 to 45 minutes."

The committee members questioned the chief of the Secret Intelligence Service, Sir Richard Dearlove, on the claim and was told the sourcing was regarded as reliable.

"The senior military officer named and quoted in the [JIC] report was in a position to comment on the deployment of chemical and biological weapons," said the report.

However, it was not backed up by similar intelligence from any other sources.

And publishing the 45 minute claim in the dossier without clarification that it referred to battlefield munitions was "unhelpful".

The government's dossier also claimed that Iraq had intended to obtain "significant quantities of uranium from Africa".

This accusation has also sparked a serious row, with the White House being forced to admit that it had no intelligence of its own to back up the claim.

And the American Central Intelligence Agency accepted that President Bush should not have referred to the claim in a keynote speech setting out the case for military action against Iraq.

The UK claim was based on "two independent sources", one of which was documentary.

There was also "some sigint [signals intelligence] concerning a visit by an Iraqi official to Niger".

Questions over the accusation arose when the International Atomic Energy Agency said it had been passed forged documents purporting to be proof of Iraqi interest in purchasing uranium.

The Secret Intelligence Service, sometimes referred to as MI6, is "still conducting further investigations into this matter".

However, the forged documents did not affect judgements on the second source so "SIS continues to believe that the Iraqis were attempting to negotiate the purchase of uranium from Niger".

"We have questioned the SIS about the basis of its judgement and conclude that it is reasonable", said the committee report.