He is one of cinema's giants, but Orson Welles looked down on many of his fellow actors and directors, viciously denigrating some of the biggest names of his day, previously unpublished private conversations reveal.

Laurence Olivier was "stupid", Spencer Tracy "hateful" and Charlie Chaplin "arrogant", and he could not even bear to look at Bette Davis. James Stewart was a "bad actor", Joan Fontaine had "two expressions, and that's it", and Norma Shearer was "one of the most minimally talented ladies to appear on the silver screen".

His criticisms have emerged from long-lost tapes in which he chatted unguardedly to a friend, never expecting them to be made public. He died suddenly in 1985 before he could edit them into a planned autobiography, and the tapes have been in the friend's garage until now.

As an actor, director, producer and writer, Welles's masterpieces include Citizen Kane, which remains one of cinema's most influential films. The interviews were recorded over regular lunches from 1983 with his friend, director Henry Jaglom. Welles died of a heart attack just days after their last meeting. Now the interviews are to be published on 16 July in My Lunches with Orson. The tapes were made available to film historian Peter Biskind, who told the Observer that they reveal Welles as never before – talking intimately about the highs and lows of his career and the people he knew. The subjects are wide-ranging – from politics to literature.

They show a cinematic genius "with his hair down", Biskind said: "He's not the great director being interviewed by a starry-eyed journalist. He's speaking to a friend, and is therefore free to gossip."

Welles lavished praise on actors he admired such as Joseph Cotten, his co-star in The Third Man ("brilliant") and John Wayne ("some of the best manners of almost any actor I've ever met in Hollywood"). But at others he hurled insults. At one point another titan of acting, Richard Burton, approached him in the restaurant, saying: "Elizabeth [Taylor] is with me. She so much wants to meet you. Can I bring her over?" Welles replied: "No. As you can see, I'm in the middle of my lunch." Jaglom scolded Welles for rudeness, observing that Burton "actually backed away, like a whipped puppy". Welles retorted: "Burton had great talent. He's ruined his great gifts. He's become a joke with a celebrity wife. Now he just works for money, does the worst shit."

Welles's stubborn insistence on his own way made it impossible for him to work within the studio system, and he struggled for funding for his films. He said about his last decade: "I have to make pictures … much cheaper – [requiring] more ingenuity and faking … yet they will be judged by the standards of the time when I had more money."

Elsewhere, he mentioned Marilyn Monroe: "She was a girlfriend … I used to take her to parties before she was a star … I wanted to try and promote her career. Nobody even glanced at Marilyn." He pointed her out to Darryl F Zanuck, the movie mogul, who commented: "She's just another stock player. We've got a hundred of them." A few months later, Zanuck had certainly noticed her .

Welles's extreme disdain for several actresses emerges repeatedly. "I never could stand looking at Bette Davis, so I don't want to see her act," he said, also dismissing Oscar-winning actress Jennifer Jones as "hopeless".

He ridiculed Humphrey Bogart for "picking fights in nightclubs" and referred to Olivier's first two scenes of King Lear on the BBC as "the worst things I ever saw in my life". He particularly loathed Spencer Tracy: "I'm having a hard time trying to think of a great Tracy performance ... He was gigantic in Judgment at Nuremberg, although it is not a great picture", but he "couldn't stand" those romantic Katharine Hepburn "things". "He was just a hateful, hateful man."

Among directors, he admired Carol Reed, for whom he played Harry Lime in The Third Man. The screenplay was written by Graham Greene, who subsequently published the book of the same name (which he had originally written as a preparation for the screenplay). Welles played down Greene's contribution: "His authorship is greatly exaggerated … Graham wrote the novel after the movie."

He had mixed views of Alfred Hitchcock: "I've never understood the cult of Hitchcock. Particularly the late American movies … Egotism and laziness. And they're all lit like television shows … I saw one of the worst movies I've ever seen the other night [Rear Window] … Complete insensitivity to what a story about voyeurism could be. I'll tell you what is astonishing. To discover that Jimmy Stewart can be a bad actor … Even Grace Kelly is better than Jimmy, who's overacting."

Biskind said: "Eavesdropping on Welles and Jaglom is [like] sitting at the table … Welles comes off as a fascinating bundle of contradictions, at once belligerent and almost childishly vulnerable … a shy man who hid behind … masks but loved to display himself."