Mrs Blair, a human rights lawyer, has long been the subject of claims about her fondness for weird and wonderful treatments, ranging from a Mayan rebirthing ceremony to eating strawberry leaves to cure swollen ankles.
But a book published yesterday about the Blairs has taken tales of odd practices inside the prime ministerial household to new extremes.
Such was the eyebrow-raising nature of the claims made in Tony And Cherie, A Special Relationship that Downing Street issued a forthright denial.
The book, written by Paul Scott, a journalist, uses alleged conversations with members of the couple's entourage to paint a picture of Mrs Blair as ambitious and intelligent but in the thrall of a series of bizarre practices. Among the techniques said to be employed by Mrs Blair was to take jars containing hair and nail clippings belonging to herself and her husband to Jack Temple, a retired market gardener turned health guru.
Temple, who died in 2004, is claimed to have "dowsed" the jars by waving a pendulum over them to detect "poisons and blockages" that could affect the Blairs.
Quoting a number of unnamed "Blair court insiders", the book claims: "Temple told Cherie that his pendulum could tell her when it was a good time or bad time to make major decisions."
The author, who also makes lurid claims about the Blairs' sex life, said he had written the book because of the way the couple had sought to portray themselves in the public eye.
Scott, who has written for the Daily Mail, said: "The Blairs have sold themselves as a ... sort of celebrity couple. It is important that in the face of this carefully-constructed image we know what goes on behind the scenes."
The couple's relationship with Carole Caplin, the former glamour model turned lifestyle adviser, is also revisited in the book, which claims that Ms Caplin personally bathed Mrs Blair as part of her service.
Scott also claims that Mrs Blair has been locked in a feud with the Princess Royal since they first met in the wake of Labour's election victory in 1997.
The Prime Minister's wife is alleged to have said: "Do call me Cherie", to which the Princess is said to have replied: "Actually, let's not go that way; let's stick to Mrs Blair."
When they met again a few years later, the Princess is claimed to have turned her back on Mrs Blair, prompting her to remark: "That bitch completely blanked me."
Downing Street has reversed its usual policy of silence on the Blairs' private life to rubbish the claims. A spokeswoman said: "This is a mixture of recycled gossip and pure fantasy; in particular the remarks about Mrs Blair and the Royal Family, which are totally untrue."
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