Brady, who is serving life for the murders and says he will never apply to be released, sent the letter to Home Secretary Jack Straw on the day that Hindley began a High Court action to overturn a decision to make a "whole life" tariff prisoner.
In the letter, issued through a news agency, he says that Hindley, 55, and he had been in love and that she had regarded the killings as "marriage ceremonies theoretically binding us ever closer. He adds: "... Existential philosophy melded with the spirituality of death and became predominant. We experimented with the concept of total possibility.
"... Before entering the witness box I instructed both her counsel and my own to ask me specific questions designed to give the fullest opportunity of providing a cover for Myra. This managed to get her off on one murder charge I also told her to adopt a distancing strategy when she went into the witness box, admitting to minor crimes whilst denying major ... For 20 years I continued to ratify the cover I had given her at the trial whilst, in contrast, she systematically began to fabricate upon it to my detriment.
"Therefore, when I learnt from the Panorama programme this week that she was now claiming I had threatened to kill her if she did not participate in the moors murders, I considered that the lowest lie of all. The fact that she continued to write several lengthy letters a week to me for seven years after we were imprisoned contradicts this cynical allegation.
"... As for the parole board, I advised her to build on three pillars: educational studies, powerful contacts and religion. She did ... In the ... Panorama programme, former Home Office minister A Widdecombe stated there are 23 prisoners in the UK who will never be released. Why has the public heard so little of them?
"In this and other special hospital run by prison warders there are also patients no one has heard of, who have been rotting behind bars for 40 and 50 years for relatively minor offences. That puts the present loud debate over Myra Hindley in proper perspective ..."Reuse content