London - Tiny alien UFOs disguised as flies, mosquitos and species butterflies such as the Common [Fire 'n'] Brimstone were the top suspects behind the PM's fears.
Newly declassified UFO files released today describe how the Blairs fought a concerted rearguard action to combat suspected 'alien stalking' during their decade at No 10.
Top weapons included harnessing the awesome anti-alien powers of New Age guru Jack Temple, roped in to ward off evil influences 'following [a personal recommendation from] the Dalai Llama'.
A favorite of Sarah, Duchess of York's own foibles Temple kitted out Cherie with a formidable array of cosmic tools to fight those alien 'assimilation' fears.
These included bizarre amulets and bio-electric shields filled with 'a matrix of specially-embellished crystals' thought to be quartz charged with cocooning Mrs Blair in a formidable alien repellant.
Temple's neolithic stone circle at his Surrey back yard was the scene of countless alien detox rites featuring healing potions made of strawberry leaves and agar agar [ugh!].
However the deep-pore cleansing did nothing to remove 'alien angst' thought to be triggered by over-zealous waxings of Cherie's mustache at a Balham salon run by Goths.
The Blairs were subsequently 'rebirthed' at another nutjob's Mexican Riviera retreat in a quaint mudbath ritual involving chanting and watermelon [don't ask!].
"Of course much of these details have been erased prior to today's release of the UFO files," a National Records source commented today.
"Wanna see footage of Tony's naked initiation at Camp David circa 2001??"