The documentary – Diana: In Her Own Words – features Diana speaking candidly about every facet of her life, in tapes recorded by her speech coach Peter Settelen, including the role of Camilla Parker Bowles in her marriage.
They have never before been broadcasted on British television and their release has been criticised by those close to the princess.
Paul Burrell, who served as a butler to Diana, blasted the broadcasting of the tapes as “a step too far”.
Mr Burrell told ITV Yorkshire: “I think those tapes were made privately for the Princess' own use… I don't think they should be broadcast.
GETTYPaul Burrell published his book on Diana, A Royal Duty, in 2003Related articles
“It's almost like raiding her diary. That's wrong... It can only upset Prince William and Prince Harry.
“I understand that there is a thirst for new information but I think it's a step too far.”
He added: “We all need to draw a line underneath it, remember the good times… It's not going back into the past and delving through laundry and seedy tapes and thoughts that were never meant to be made public.”
The content of the tapes was regarded as so sensitive that the prosecution agreed not to use them in the trial of the former–royal butler which subsequently collapsed.
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Unseen pictures of a young Princess Diana from her private family photo album
GETTYThe tapes were recorded by her speech coach Peter Settelen
It's almost like raiding her diary. That's wrong
Mr Burrell sparked anger from Prince William and Harry after he published the book on Dian titled A Royal Duty in 2003.
William and Harry, just 21 and 19 at the time, said: “We cannot believe that Paul, who was