Downing Street has described as "highly significant" a report from an independent think tank saying Iraq could produce a nuclear bomb within months.

The International Institute for Strategic Studies (IISS) says Saddam Hussein would first need to obtain supplies of radioactive material.

We are obviously not talking about washing powder here

Downing Street on Iraq's biological weapons

The IISS in London also concludes Iraq has probably been successful in hiding large stockpiles of chemical and biological weapons from United Nations inspectors, as well as a small number of long-range missiles.

Iraq's official press have dismissed the suggestion the country has weapons of mass destruction (WMD) as "a Zionist-inspired pack of lies".

The Iraqi Government let journalists to a former nuclear site on Monday to underline their claims about how it is now being put to peaceful use.

Dossier debate

Downing Street says its own dossier of evidence against Iraq would be published shortly, but said the latest report "paints a powerful picture of a highly unstable regime".

A spokesman also confirmed Mr Blair discussed Iraq on Monday with the leaders of Canada and France, Prime Minister Jean Chretien and President Jacques Chirac.

Prime Minister Tony Blair's official spokesman said debate continued about how much could be put into the dossier without jeopardising intelligence sources.

Blair says he is confident he can win around international opinion

"This is clearly a very serious piece of work. It has been produced without any access to intelligence materials," said the spokesman.

The spokesman warned against "language fatigue" over descriptions of chemical and biological weapons.

"We're obviously not talking about washing powder here," he added.

War talk?

The report will fuel speculation about possible US-led military action against Iraq.

Defence expert Paul Beaver said the report was the best compilation of the facts he had seen.

"But there's nothing new here, no killer fact that makes me believe that we should go to war tomorrow," added Mr Beaver.

Iraq has rubbished claims that it has weapons of mass destruction

On Sunday, Mr Blair returned from a meeting with the US President George Bush resolute on tackling the Iraqi "threat", but facing mounting opposition at home.

Former senior UN weapons inspector in Iraq, Scott Ritter, told politicians in Baghdad that their country was not a threat to the rest of the world and military action against it would be unjustified.

The IISS report, unveiled by its author Dr John Chipman on Monday, attempts to sift the available evidence and use the expertise of former weapons inspectors to assess Iraq capability.

It stresses there are gaps in the information as weapons inspectors left Iraq in 1998 after making significant discoveries.

The report says:

• It is not clear how much the Iraqis concealed from inspectors in 1998
• It would be "incredible" if there had not been more weapons efforts since then
• Iraq has up to 12 Al-Hussein weapons with a 650km range

Shared strategy

The IISS also suggests Iraqi scientists still have the necessary knowledge and experience - and in some cases the materials - to reconstruct biological and chemical weapons programmes.

The IISS does not believe that Iraq yet has the necessary fissile building-blocks for a nuclear bomb.

However, it warns that Iraq could build such a weapon within a matter of months if it were able to obtain the necessary radioactive materials.

Returning from Camp David, Mr Blair said he and President George Bush had developed a "shared strategy" based on a determination that the country's weapons of mass destruction must be destroyed.

On Tuesday, he will use a speech to the Trade Union Congress to push for action.

Emergency debate

Mr Blair will say that, while the United Nations should deal with the issue, Saddam Hussein cannot be allowed to flout its resolutions "year after year, after year".

That warning comes ahead of President Bush's speech to the UN in New York on Thursday.

The prime minister is also planning to brief senior MPs over the coming weeks but many Labour politicians are yet to be convinced of the case for military action.

Father of the House of Commons, Tam Dalyell, is among those who want MPs recalled to Westminster for an emergency parliamentary debate.

Conservative leader Iain Duncan Smith instead argued the IISS report underlined the need to act.

"If we don't deal with him now and force him to get rid of his weapons then we could be all faced with a very, very serious problem in the next couple of years," he told Sky News.

But Liberal Democrat foreign affairs spokesman Menzies Campbell said there was "nothing startling" in the report and more would be needed to sway public opinion.