LONDON, Sept. 24 — Britain today published a long-awaited dossier asserting that the regime of President Saddam Hussein of Iraq was continuing to expand stockpiles of chemical and biological weapons and had plans to use them. Arguing for urgent action by the West, it said that some of the weapons could be deployed within 45 minutes.

The 50-page document also asserted that there was intelligence information that Iraq was trying to acquire materials abroad to build nuclear weapons and had extended the range of its ballistic missiles as part of a plan to menace and dominate its own region.

The dossier was released hours before the opening of a debate in Parliament on Britain's aggressive stance on Iraq and Prime Minister Tony Blair's apparent endorsement of the Bush administration's vow to take action against Mr. Hussein if the United Nations does not rise to the challenge.

Mr. Blair, the president's staunchest ally in Europe, was obliged earlier this month to summon the lawmakers back from summer recess for a one-day special session after many of them, mostly from his own Labor Party, raised doubts about Britain's involvement in an anti-Iraq military campaign.

One of the most prominent skeptics, the Labor legislator Diane Abbott, said the report was unpersuasive and offered nothing new.

"Tony Blair will have to do better than this if he wants to convince the British public to go to war," she said. Protesters in an open-top bus outside the House of Commons loudly sang John Lennon's "Give Peace a Chance."

In Baghdad, an Iraqi government minister denied all the charges.

"Mr. Blair is acting as part of the Zionist campaign against Iraq and all his claims are baseless," Culture Minister Hamed Yousif Hummadi said at a news conference.

An adviser to Mr. Hussein, Lt. Gen. Amir al-Sadi, called the Blair report "a hodgepodge of half-truths, lies, shortsighted and naive allegations" that would not hold up after an investigation by "competent and independent" experts. He also denied that the range of its missiles was being extended beyond limits laid down by the United Nations, as the report claimed.

Reaction from the White House to the Blair presentation was highly supportive, prompting President Bush at a cabinet meeting this morning to repeat his call for early action by Congress on a resolution "to hold Saddam Hussein to account for a decade of defiance."

Mr. Bush called Mr. Blair a very strong leader and said he admired his willingness "to tell the truth and to lead."

The White House spokesman, Ari Fleischer, called Mr. Blair's speech "very bold," adding that the dossier was "frightening in terms of Iraq's intentions and abilities to acquire weapons."

In a foreword to the 50-page dossier, Mr. Blair said he believed that the compilation of information from Britain's intelligence and security agencies had proved that Mr. Hussein threatened the stability of the world and had to be blocked now.

"What I believe the assessed intelligence has established beyond doubt is that Saddam has continued to produce chemical and biological weapons, that he continues in his efforts to develop nuclear weapons and that he has been able to extend the range of his ballistic missile program," he said. "I also believe that, as stated in the document, Saddam will now do his utmost to try to conceal his weapons from U.N. inspectors."

In a bid to get international support for moving against Iraq, the United States and Britain are preparing a new United Nations resolution that would oblige Mr. Hussein to disarm and threaten military action if he did not. Mr. Blair said the measure was just "days away."

Seeking to sway the opinions of the many critics in Britain who agree that Mr. Hussein is dangerous but believe he has been effectively contained and question the need to attack him now, Mr. Blair said:

"It is clear that, despite sanctions, the policy of containment has not worked sufficiently well to prevent Saddam from developing these weapons. I am in no doubt that the threat is serious and current, that he has made progress on weapons of mass destruction and that he has to be stopped."

In an implied response to criticism that he has hewed too closely to the Bush administration's militant stance on Iraq, he said: "I believe that faced with the information available to me, the U.K. government has been right to support the demands that this issue be confronted and dealt with."

The dossier did not say that Iraq had a present nuclear ability but asserted that Mr. Hussein had sought significant quantities of uranium from Africa despite having no civilian nuclear program that could use it and had recalled specialists to work on his nuclear program. The dossier estimated that Mr. Hussein would need five years to develop a nuclear weapon on his own but could speed the process to within two years if he acquired weapons grade material.

It also asserted that Iraq had rebuilt chemical plants destroyed in the 1991 Persian Gulf war and had developed mobile laboratories for making biological weapons that could be used in warfare to escape detection and attack invading troops.

The report said Mr. Hussein had retained up to 20 al-Hussein missiles with a range of 400 miles, capable of carrying chemical or biological weapons, and it published a map showing that Iraqi weapons under development could reach the whole of the Arab Middle East, Israel, Greece and Turkey. A report by the London-based International Institute of Strategic Studies earlier this month put the number of al-Husseins at 12.

John Chipman, director of the institute, said today that the government's assessment also disclosed new details about Mr. Hussein's efforts to procure materials abroad for its nuclear program and highlighted Iraq's strategy for confounding new inspections.

"It shows that Iraq has prepared for the possible return of inspectors by developing more sophisticated concealment strategies," he told the BBC.

The dossier repeated claims in other recent reports that Mr. Hussein regards weapons of mass destruction not as weapons of last resort but as useable bombs and missiles capable of giving Iraq regional power.

The British public has shown in polls that it is insistent that any action against Iraq be taken only with United Nations approval, and the dossier went out of its way to portray Mr. Hussein as constantly and flagrantly in violation of United Nations rules and resolutions.

In one of the more original entries, the dossier makes its case for Mr. Hussein's diversion of largesse to his own comfort by publishing a drawing of one of his vast presidential palaces overlaid on the distinctly smaller area taken up by Buckingham Palace, the official residence of British monarchs.

Attacking Mr. Hussein's human rights record, the dossier included claims that prisoners in Iraq are executed without trial or left in metal boxes to die if they do not confess, women held in prison are routinely raped by guards and people accused of slandering Mr. Hussein have their tongues removed.

It also included graphic pictures of Kurdish children killed by Iraqi chemical weapons in 1988, and Mr. Blair singled out these passages in opening the Commons debate.

"Read it all and again I defy anyone to say that this cruel and sadistic dictator should be allowed any possibility of getting his hands on more chemical, biological or even nuclear weapons," he declared.

The dossier said that Mr. Hussein was able in 2001 to make $3 billion in "illicit earnings" despite United Nations sanctions and that he was on track to raise the same amount this year. The money, meant to go to relief causes, was instead devoted to development of weapons of mass destruction, it said.

As for longer range missiles, the report said Iraq is developing both its al-Samoud liquid-propellant and its Ababil-100 solid-propellant missiles and extending their ranges to 125 miles, beyond the 93 miles limit set by the United Nations.

Mr. Blair began this afternoon's debate with a call on the international community to unite to make sure that Iraq disarms even if it takes military action to accomplish the task.

"Our case is simply this," he told Parliament. "Not that we take military action come what may. But that the case for ensuring Iraqi disarmament is overwhelming."