In a strongly worded letter, written on behalf of all Church of England bishops and seen by The Times, they say: “It is clear that the apparent breach of international law in relation to the treatment of Iraqi detainees has been deeply damaging.

“The appearance of double standards inevitably diminishes the credibility of Western governments with the people of Iraq and of the Islamic world more generally.

“More fundamentally still, there is a wider risk to our own integrity if we no longer experience a sense of moral shock at the enormity of what appears to have been inflicted on those who were in the custody of Western security forces.” The letter, written with the unanimous support of all the Church’s 120 diocesan, suffragan and assistant bishops, who met in Liverpool this month, was sent to the Prime Minister on Friday. It was timed to coincide with the handover of power in Iraq.

Downing Street confirmed last night that it had been received. An official said: “The archbishops are entitled to their views and the Prime Minsiter will reply in due course.”

The archbishops also say that the reputation of Britain as “honest brokers” in the Israeli-Palestinian conflict must not be jeopardised. They are understood to be concerned by the growing influence of Christian Zionists in the Christian community and the US Administration.

Anglican bishops showed a rare unanimity in condemning the Iraq war from the start. In a sermon in Cambridge recently, Dr Williams said that Mr Blair was in danger of eroding public trust in Britain’s political system.

This latest intervention, designed to influence the conduct of Western security for-ces, is the strongest to date. It is more usual for the bishops to use their 26 seats in the House of Lords to influence political events. It indicates the strength of feeling that they bypassed this system.

One source said: “I cannot remember the two archbishops writing directly to the Prime Minister in this manner before.”

Dr Williams and Dr Hope insist that the priority must be to do everything possible to help the Iraqi people to rebuild their country. For this, they say, it is essential to maintain the rule of law.

They continue: “The credibility of coalition partners in advocating respect for the law and the peaceful resolution of disputes will, we fear, be undermined unless the necessary moral authority is clearly demonstrated at every level.”

One of their main concerns is the damage caused by the conflict to community relations in Britain between Muslims and non-Muslims. Some of the strongest advocates for the letter were bishops from cities with large Muslim populations, such as Bradford.

They are concerned by a rise in Islamophobia and fear that the September 11 attacks have desensitised emotions so that the treatment meted out to detainees no longer causes the moral outrage it should.

In their letter, the two archbishops welcome the assurances of the British and US authorities that those responsible for the abuses will be brought to justice. But they say: “Nevertheless, there remain serious questions over how such brutal and indecent behaviour could have come about.”

Citing the Arab-Israeli conflict as another “litmus test” of the Blair Government’s respect for human rights and international agreements, they argue that the legacy of British commitment to respect both sides has enabled the UK to be accepted as “honest brokers”. They continue: “It is vitally important that this position is not eroded.”

In a guarded reference to the growing influence of the Christian Zionist movement in the US — which takes the view that the restoration of the biblical Israel is necessary to facilitate the Second Coming of Christ — the archbishops admit: “Within the wider Christian community we also have theological work to do to counter those interpretations of Scripture from outside the mainstream of the tradition which appear to have become increasingly influential in fostering an uncritical and one-sided approach to the future of the Holy Land.”

A Church of England spokesman said last night: “The letter was not written for publication, but was intended as a positive contribution to the development of government policy.”

END