According to this BBC report in the run up to the Iraq war the UK’s Secret Intelligence Service (often mis-identified as MI6) was open within UK government circles about their lack of knowledge of what was going on in Iraq.
When Lord Butler spoke in the House of Lords in February 2007 he quoted from an intelligence report dated 22nd August 2002 which said:
we … know little about Iraq’s chemical and biological weapons work since late 1988
Pretty concise and easy to understand you would have thought – and yet somehow over the next month that got spun into “extensive, detailed and authoritative” intelligence when Tony Blair reported it to the House of Commons on the 24th September 2002.
I am aware, of course, that people will have to take elements of this on the good faith of our intelligence services, but this is what they are telling me, the British Prime Minister, and my senior colleagues. The intelligence picture that they paint is one accumulated over the last four years. It is extensive, detailed and authoritative. It concludes that Iraq has chemical and biological weapons, that Saddam has continued to produce them, that he has existing and active military plans for the use of chemical and biological weapons, which could be activated within 45 minutes, including against his own Shia population, and that he is actively trying to acquire nuclear weapons capability.
Those words could simply not have been justified by the material that the intelligence community provided to him.
So by misrepresenting what the intelligence community said he has completely blown the chance of people in future believing real reports of danger that come via those agencies. So Blair, Bush and Howard have become “the boys that cried wolf” and we are all less safe for it.