Dr Rowan Williams, the Archbishop of Canterbury, today launched a powerful and unprecedented attack on the Government over its policy in Iraq.
He accused Tony Blair and his ministers of rushing into the war, of not being sufficiently truthful and of creating "a weakening of trust in the political system of our nation".
Arguing that trust could be restored by the admission of error or miscalculation, Dr Williams even made a case for civil disobedience, arguing that political obedience in our age has become "problematic". Anglican theologians have never sanctioned compliance with "unjust law", he said.
Dr Williams was preaching the university sermon at St Benet’s Church, Cambridge. The sermon was endowed by John Mere, a fellow of Corpus Christi, more than four centuries ago to teach "due obedyence of the subjectes to their princyes".
Dr Williams has often made clear that, along with with nearly all religious leaders in Britain, he was opposed to the war in Iraq, but he has never before been openly critical of the present Government on this or any other policy.
Invited two years ago to deliver the Mere Commemoration sermon, he has been developing his argument for some months in the light of the events of last year.
While appearing to advocate civil disobedience, sources close to him made clear that this should only occur in the most extreme circumstances and the UK was not yet at that point.
The example he used in his sermon was of the American civil rights movement. Dr Williams said that Christian political obedience must rest on confidence in a government's capacity for attention.
He condemned the "idle and selfish hearts" of those who advocate Christian obedience while themselves being slow to bring their own thoughts "under obedience to Christ".
Dr Williams said: "Part of the continuing damage to our political health in this country has to do with a sense of the events of the last year on the international scene being driven by something other than attention.
"There were things government believed it knew and claimed to know on a privileged basis which, it emerged, were anything but certain. There were things which regional experts and others knew which seemed not to have received attention."
Dr Williams, a former lecturer in divinity at Cambridge, addressing a congregation of academics, clerics and students, continued: "Forgetting the melodramatic language of public deception, which is often just another means of not attending to what is difficult and takes time to fathom, the evidence suggests to many that obedience to a complex truth suffered from a sense of urgency that made attention harder."
He indicated that the Government had, by its behaviour over Iraq, lost its right to obedience from its citizens.
"We do not usually look in our rulers for signs of advanced contemplative practice. Nor do we say, even as Christians, that no obedience is due to unbelieving governments.
"But we do say that credible claims on our political loyalty have something to do with a demonstrable attention truth, even unwelcome truth."
Dr Williams continued: "A government that habitually ignored expert advice, habitually pressed its interests abroad in ways that ignored manifest needs and priorities in the wider human and non-human environment, habitually repressed criticism or manipulated public media, such a regime would, to say the least, jeopardise its claim too obedience because it was refusing attention."
Such a government "would be concerned finally about control and no more, and so would be a threat to its citizens and others".
Making the case for an apology from the Government or at least an admission of error, he said: "Governments, of whatever kind, restore lost trust above all by their willingness to attend to what lies beyond the urgency of asserting control and retaining visible and simple initiative, by patient accountability and the freedom to think again, even to admit error or miscalculation.
"Happy the person or the government that can simply find the right, the inevitable gesture that fully fits the truth of circumstances as gracefully as the scoring of a goal."
Dr Williams said Christian obedience must be an "intelligent obedience" that involved a careful questioning.
"Whatever may have been the theology of obedience in past ages, we cannot now ignore the democratisation of knowledge and the deepened awareness of how ideological distortions may be sustained in public life."
He said it was right that claims for obedience should be tested fairly, although not out of a corrosive cynicism about power.
"It is not that we need to claim the right to remake for ourselves every decision government makes for us. That is a trivialising of democratic government, though one that is very typical of our current scene.
"It is possible to accept a government decision as lawful and proper even when I disagree, because I recognise that a process has been undertaken that has some right to be called attentive."
People had a vote they could exercise at elections, he conceded. "But without these processes being robust and visible and involving more than just simple governmental interest at any time, the authority of government suffers. It is not that we face regular campaigns of huge public disobedience.
"There may be a time for these, as in the Civil Rights struggles of sixties America. But they are rightly rare, confined to cases where government’s inattention has become a matter of serious and lasting injustice.
"It is more that we face a general weakening of trust in the political system of our nation."
The sermon was welcomed by members of the congregation. Dr David Ford, Regius Professor of Divinity at Cambridge, said: "It was a well-crafted, judicious and timely contribution to the highest level of political discussion in this country."