Toppling Saddam Hussein from power was being discussed by British and US officials two years before the invasion of Iraq, senior Whitehall figures admitted yesterday.

Foreign Office mandarins even drew up a secret document discussing the idea of removing the dictator as attempts to restrain him with sanctions began to fail. But any suggestions of supporting "regime change" were dismissed repeatedly as having no legal backing.

On its opening day of public hearings, Sir John Chilcot's inquiry into the Iraq war heard that elements of President Bush's administration, which came to power at the start of 2001, were already making noises in support of regime change in Iraq even before the 9/11 terror attacks in the US.

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Senior figures working in the Foreign Office and the Ministry of Defence during the period said that regime change "was mentioned" during secret meetings between US and British officials during 2001. They also revealed that there was already a "drum beat" for war in Iraq from elements of the US administration at that point.

They explained that sanctions against Saddam Hussein had been breaking down, leaving the Iraqi leader "quite comfortable", with a growing income, which caused concern in London and Washington. However, removing him was not then considered a legal route and official policy was to contain the actions of the Baghdad regime.

Secret regime change paper

Sir William Patey, a former Foreign Office official, said that he had gone as far as commissioning a paper setting out regime change as one of a variety of options in dealing with Iraq. The internal Foreign Office memo was never released and references to regime change were removed once it was passed on to the Cabinet Office for further discussion.

"This is a paper I commissioned from my staff and said 'Let's have the whole range of options out here'," said Sir William. The document discussed "hard containment to 'soft' containment, to the lifting of sanctions, to – I have to say – the regime-change option, which was dismissed at the time as having no basis in law." He added: "It was very much an internal paper."

Sir Peter Ricketts, who was chairman of the Joint Intelligence Committee (JIC), said that in those early days, it was Britain and the US which were most worried about the threat posed by Saddam. "I think the sense of the threat was probably sharpest in London and Washington," he said. But he made clear that in 2001, regime change "was something that we thought there could be no legal basis for".

Sanctions failing

He said that concerns had emerged that the strategy of attempting simply to "contain" Saddam Hussein was failing. The combination of strict sanctions, no fly-zones and an "oil-for-food" programme, had been used since the 1990-91 Gulf War. But extensive smuggling meant the policy was "in trouble".

Britain's hopes of creating a new "smart sanctions regime", initially backed by elements of the US administration, were fiercely opposed by Russia because of their "commercial interests" in Iraq. Repeated attempts to reach an agreement during 2001 failed.

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Meanwhile, Sir Peter added that he was "conscious that there were other voices in Washington, some of whom were talking about regime change". In particular, he pointed to an academic article written in 2000 by President Bush's National Security Adviser, Condoleezza Rice, which warned that "nothing will change" in Iraq until Saddam was removed from power. Sir William added: "We were aware of these drum beats from Washington and internally we discussed it. Our policy was to stay away from that."

He said that diplomats from other countries were aware that the failure to reach a new agreement on sanctions during the summer of 2001 could lead to tougher action from the US.

The effect of 9/11

The inquiry heard that, while US policy in Iraq had been controlled by Colin Powell and the State Department during the summer of 2001, there was a "dramatic" hardening of support for regime change when power transferred to the Pentagon and the hawkish Defence Secretary, Donald Rumsfeld, in the wake of the 9/11 attacks.

"We heard that people in Washington thought there might be some link between Saddam Hussein and Osama bin Laden – undocumented," Sir Peter said. "I don't think we saw any evidence of it. The tone of voice was more if there turns out to be any link between Saddam Hussein and Osama bin Laden that is going to have major implications for Iraq and Saddam Hussein."

Both the British and US governments suddenly made anti-terrorism their highest priority, with heightened concerns over the availability of weapons of mass destruction, the inquiry was told. According to Sir Simon Webb, then a policy director at the Ministry of Defence, the shift in emphasis led to military action in Iraq being pushed up the agenda. "The shift in thinking was to say that we cannot afford to wait for these threats to materialise. We must be ready to engage potential threats wherever they emerge," he said.

"The focus didn't shift to regime change. It shifted to the weapons of mass destruction problem. In the case of Iraq, in order to deal with [this] problem, you would probably end up having to push Saddam Hussein out of power."

However, Sir Peter insisted that, while 9/11 had increased fears of weapons of mass destruction falling into the wrong hands, it had not yet shifted British policy to one of support for ousting Saddam Hussein. "We still had our focus on the weapons inspector route and the sanctions-type route," he said. "We had heard these noises about regime change. They weren't really impinging on the Whitehall policy debate at that point."

No one on trial

In his opening remarks, Sir John disappointed critics of the Iraq invasion by insisting that no politicians, military figures or civil servants would be found guilty by his inquiry. He said that nobody was "on trial" and that it was not the job of his committee to decide the "guilt or innocence" of those who led Britain into war. Tony Blair will be among those giving evidence.

Sir John attempted to reassure sceptics that his team would not "shy away from making criticisms where they are warranted". The retired civil servant also hit back at criticism that those on the inquiry team were too closely associated with the establishment. "My colleagues and I come to this task with open minds," he said. "We are apolitical and independent of any political party. We want to examine the evidence."

Mr Blair is expected to be called to give evidence early in the new year. Gordon Brown's spokesman said that the Prime Minister would "of course" be willing to appear as a witness, but had not yet been asked to do so. "The Prime Minister completely supports the inquiry," the spokesman added. "He's very pleased it's going ahead."

Iraq and the West: The long road to regime change

2 August 1990 Iraq invades Kuwait leading to condemnation by the UN Security Council which demands a full withdrawal.

16-17 January 1991 Coalition forces begin aerial bombing of Iraq.

27 February Kuwait is liberated after three-day ground operation.

16-19 December 1998 UN inspection team is withdrawn, after concluding that Iraq is not co-operating fully.

February 2001 Britain and US bomb Iraq's air defence network.

30 January 2002 In the first State of the Union address after 9/11, US President George W Bush says Iraq is part of an "axis of evil".

3 September Tony Blair says he is "in absolute agreement" with the US that Iraq "poses a real and a unique threat to the region and rest of the world".

12 September President Bush addresses UN to put the case for war against Iraq.

24 September Britain publishes dossier saying Iraq could produce a nuclear weapon in one or two years.

13 January 2003 Blair says Britain could act against Iraq with the US and without a second UN resolution.

3 February UK Government publishes fresh dossier of evidence of Iraq WMD.

15 February More than 750,000 people march through London in protest against the war.

26 September 121 Labour MPs vote against Tony Blair's war strategy after an impassioned debate on Iraq.

20 March Start ofUS campaign to topple Saddam Hussein. British ground troops enter Iraq.

9 April Baghdad falls to US forces.

29 May BBC reporter Andrew Gilligan suggests the first-draft of the Iraq dossier was 'sexed up' under executive orders.

7 July MoD scientist David Kelly named as Gilligan's source.

18 July Dr Kelly is found dead with slashed wrists.

14 December Saddam Hussein is captured in Tikrit, hiding in a tiny bunker.

28 January 2004 Lord Hutton's report finds Dr Kelly took his own life, clearing the Government of "sexing up" the dossier and condemning the BBC.

14 February Lord Butler's inquiry into intelligence on Iraq's weapons finds it was "sporadic and patchy".

October 2005 Saddam Hussein is found guilty of crimes against humanity. He is executed two months later.

12 March 2007 Former UN chief weapons inspector Hans Blix accuses Tony Blair of "exercising spin" in the run-up to the war.

December Britain hands over security of Basra province to Iraqi forces.

November Iraqi parliament approves security pact with America under which all US troops are due to leave the country by the end of 2011.

March 2009 US President Barack Obama announces withdrawal of most US troops by end of August 2010.

June US troops withdraw from towns and cities in Iraq.

November Independent inquiry chaired by Sir John Chilcot begins.