Guardian is reporting the Coulson, Cameron's one time press secretary may have been shown top secret documents he shouldn't have seen because those around him didn't know that he didn't receive appropriate vetting. His lack of a thorough vetting strengthens suspicions that Cameron was ordered by Rebecca Brooks to hire Coulson and the only way to do that given the allegations against him was to circumvent the normal vetting procedure.
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Senior government officials working with Andy Coulson believed that he did have the highest security clearance, it is claimed, raising questions over whether the prime minister's former aide was improperly granted access to the most sensitive information.
Last week it emerged that the former editor of the News of the World had not undergone the most intensive vetting on becoming the prime minister's director of communications and so was working without the highest level of clearance. This should have restricted his access to some documents.
But Labour MP Chris Bryant told the Observer that he had been informed by senior officials that they had believed Coulson was working with the same security clearance as had been held by Alastair Campbell, Tony Blair's press secretary, who underwent the toughest vetting procedures, which are known as DV (developed vetting).
http://www.guardian.co.uk/media/2011/jul/24/coulson-security-fears-over-vetting