Never heard before tapes of Princess Diana have revealed her true feelings about her marriage to King Charles.

The audio, recorded by Diana in the ’90s, sees her discuss her husband, her sons, and the troubled relationship with her stepmother Raine Spencer.

She recorded her thoughts for author Andrew Morton on the condition of secrecy – contents of which have been used to make the book Diana: Her True Story and will be revealed in a new documentary set to be released next year.

Snippets of the audio recordings obtained today by ABC reveal the mind of the Princess.

Speaking about her wedding day she said: “It was grown up. Here’s Diana, a kindergarten teacher. I mean the whole thing was ridiculous.”

And on the subject of Charles’s relationship with her stepmother, she revealed he “won’t even talk to mummy”.

She said: “At Harry’s christening Charles went up to mummy and said: ‘We’re so disappointed, we wanted a girl’ and mummy snapped his head off and said you should realise you are lucky to have a child that’s normal.

“Ever since that day, the shutters have come down. That’s what he does when he gets somebody answering back at him.”

Raine married Princess Diana’s father John in 1976 after her mother Frances Shand Kydd left.

After John’s death in 1992, she left the family seat of Althorp due to her strained relationship with stepson Charles.

Diana said her own relationship was at times just as strained.

She explained: “I was so angry. I said I hate you so much. If you only knew how much we all hated you for what you’ve done. You ruined the house.

“You spent daddy’s money. I have said everything I possibly could. Raine said you have no idea how much pain your mother put your father through.

“I said pain Raine? It’s one word you don’t even know how to relate to. In my job, I see people suffer like you never see. You call that pain? I said you’ve got a lot to learn.

“I remember really going for her gullet.”

Previous reports have it that Diana and her siblings did not like their stepmother and referred to her as “Acid Raine” and often sang “Raine, Raine, go away!”

The news of the documentary comes as this week marks 26 years since Diana passed away.

The People’s Princess died on August 31, 1997, after suffering fatal injuries in a car crash in the Pont de l’Alma road tunnel in Paris.