A devastating attack on Mr. Blair's justification for military action by Carne Ross, Britain's key negotiator at the UN, has been kept under wraps until now because he was threatened with being charged with breaching the Official Secrets Act.

During that time, I helped negotiate several UN Security Council resolutions on Iraq, including resolution 1284 which, inter alia, established UNMOVIC (an acronym I coined late one New York night during the year-long negotiation). I took part in policy debates within HMG and in particular with the US government. I attended many policy discussions on Iraq with the US State Department in Washington, New York and London....

I read the available UK and US intelligence on Iraq every working day for the four and a half years of my posting. This daily briefing would often comprise a thick folder of material, both humint and sigint. I also talked often and at length about Iraq's WMD to the international experts who comprised the inspectors of UNSCOM/UNMOVIC, whose views I would report to London. In addition, I was on many occasions asked to offer views in contribution to Cabinet Office assessments, including the famous WMD dossier (whose preparation began some time before my departure in June 2002).

During my posting, at no time did HMG assess that Iraq's WMD (or any other capability) posed a threat to the UK or its interests. On the contrary, it was the commonly-held view among the officials dealing with Iraq that any threat had been effectively contained. I remember on several occasions the UK team stating this view in terms during our discussions with the US (who agreed). (At the same time, we would frequently argue, when the US raised the subject, that "regime change" was inadvisable, primarily on the grounds that Iraq would collapse into chaos.)

Any assessment of threat has to include both capabilities and intent. Iraq's capabilities in WMD were moot: many of the UN's weapons inspectors (who, contrary to popular depiction, were impressive and professional) would tell me that they believed Iraq had no significant materiel. With the exception of some unaccounted-for Scud missiles, there was no intelligence evidence of significant holdings of CW, BW or nuclear material. Aerial or satellite surveillance was unable to get under the roofs of Iraqi facilities. We therefore had to rely on inherently unreliable human sources (who, for obvious reasons, were prone to exaggerate).

Without substantial evidence of current holdings of WMD, the key concern we pursued was that Iraq had not provided any convincing or coherent account of its past holdings. When I was briefed in London at the end of 1997 in preparation for my posting, I was told that we did not believe that Iraq had any significant WMD. The key argument therefore to maintain sanctions was that Iraq had failed to provide convincing evidence of destruction of its past stocks.

Iraq's ability to launch a WMD or any form of attack was very limited. There were approx 12 or so unaccounted-for Scud missiles; Iraq's airforce was depleted to the point of total ineffectiveness; its army was but a pale shadow of its earlier might; there was no evidence of any connection between Iraq and any terrorist organisation that might have planned an attack using Iraqi WMD (I do not recall any occasion when the question of a terrorist connection was even raised in UK/US discussions or UK internal debates).

There was moreover no intelligence or assessment during my time in the job that Iraq had any intention to launch an attack against its neighbours or the UK or US. I had many conversations with diplomats representing Iraq's neighbours. With the exception of the Israelis, none expressed any concern that they might be attacked. Instead, their concern was that sanctions, which they and we viewed as an effective means to contain Iraq, were being delegitimised by evidence of their damaging humanitarian effect.

I quizzed my colleagues in the FCO and MOD working on Iraq on several occasions about the threat assessment in the run-up to the war. None told me that any new evidence had emerged to change our assessment; what had changed was the government's determination to present available evidence in a different light. I discussed this at some length with David Kelly in late 2002, who agreed that the Number 10 WMD dossier was overstated....

I proposed on several occasions the establishment of a multinational body (a UN body, if we could get the Security Council to agree it) to police sanctions busting. I proposed coordinated action with Iraq's neighbours to pressure them to help, including by controlling imports into Iraq. I held talks with a US Treasury expert on financial sanctions, an official who had helped trace and seize Milosevic's illegal financial assets. He assured me that, given the green light, he could quickly set up a team to target Saddam's illegal accounts.