Harold Wilson's doctor plotted to kill Marcia Falkender

Harold Wilson's personal doctor suggested murdering the former prime minister's secretary when she threatened to reveal an alleged affair with Mr Wilson, it was claimed yesterday.

Dr Joe Stone offered to "dispose" of Marcia Falkender in 1975 amid panic in Downing Street over her threat to "destroy" the Prime Minister.

The allegation is made in a book by Mr Wilson's press secretary, Joe Haines.

Lady Falkender, who was given a peerage by her employer, is said to have summoned Mr Wilson's wife, Mary, in 1972 and bluntly told her of the alleged fling. Mr Wilson, who died in 1995, relayed the conversation back to Mr Haines, saying Lady Falkender had told Mary: "I have only one thing to say to you. I went to bed with your husband six times in 1956 and it wasn't satisfactory."

Unease among the Prime Minister's closest advisers grew as she repeatedly told colleagues that it would take one phone call to end his career. The concern reached a peak in 1975 when Lady Falkender was considering testifying in a libel action against the Evening Standard newspaper.

Mr Haines recalls a conversation with Dr Stone, who has since died, in which the doctor revealed he had prescribed Lady Falkender with tranquillisers and could engineer her death. Mr Haines said: "Joe was devoted to Wilson but loathed Marcia. He discussed the proposition of 'disposing of her' to take the weight of Marcia off the Prime Minister. He told me he could make it look like natural causes and sign the death certificate ... I told him there was no way in which I could go down that road."

The matter was raised again by Dr Stone a few weeks later in Bonn and again quashed, Mr Haines claimed. There was no suggestion that Mr Wilson himself was made aware of the idea.

The book, serialised in The Mail on Sunday, adds that Lady Falkender may have been allowed to stay in her post because of a successful 1965 libel action taken by Mr Wilson against the New York Herald Tribune for alleging an affair with his personal secretary.

Lady Falkender, now 70, who has always denied having had a sexual relationship with Mr Wilson, rejected the notion of a murder plot as "outrageous" and completely out of character for the doctor.