Thomas Markle, 75, claimed he felt forced to share the note, which is now at the centre of a legal battle between Meghan and the Mail on Sunday, after it was misrepresented by an article in People magazine.
The handwritten letter was published in February, but in an interview with the newspaper, Mr Markle said he kept the “hurtful” letter secret for six months and never intended to share it.
The retired lighting director said he was “devastated” when it was first mentioned publicly in the American magazine.
He said: “I decided to release parts of the letter because of the article from Meghan’s friends in People magazine. I have to defend myself. I only released parts of the letter because other parts were so painful. The letter didn’t seem loving to me. I found it hurtful.
“There was no loving message in there, nothing asking about my health, nothing from her saying, ‘Let’s get together and heal our differences’.”
People magazine quoted an anonymous friend of Meghan, claiming that the duchess felt her father did not understand her desire for privacy after he suggested they should pose together for a press photo.
Mr Markle said: “I don’t want a picture for any other reason than if we show harmony then the press will back off.
“When I opened the letter I was hoping it was the olive branch I’d longed for. I was expecting something that would be a pathway to reconciliation. Instead it was deeply hurtful.
“I was so devastated I couldn’t show it to anyone – and never would have, had it not been for the People magazine piece which meant I had to release portions to defend myself."
This week, Meghan [**began legal proceedings**](http://Was this the right moment for Harry and Meghan to announce their legal action?) against the newspaper, claiming it had breached copyright, infringed her privacy and breached the Data Protection Act by publishing the note.
The claim also alleges the paper edited the letter by “strategically omitting select paragraphs, specific sentences, and even singular words to mask the lies they had perpetuated for over a year”.
The Duke of Sussex recently accused the tabloid press of a “ruthless campaign” against his wife, adding: “I lost my mother and now I watch my wife falling victim to the same powerful forces.”
The Mail on Sunday said it intends to defend itself “vigorously” if the case ends up in court and denies changing the meaning of the document.
Proceedings initiated by Harry at the High Court on Friday in relation to the illegal interception of voicemail messages are now said to include allegations reporters and private investigators accessed Diana, Princess of Wales’ voicemails.