It is a tradition as time-honored and seedy as the movie business itself.

Indeed, many of Hollywood's biggest names secretly owe their careers to an assignation on Tinseltown's infamous 'casting couch.'

But one top insider has now suggested that some of those film stars may have enjoyed sleeping their way to the top rather more than others.

Jean-Pierre Dorléac, an Oscar-nominated costume designer, will likely outrage many by claiming that Grace Kelly was one of the biggest 'tramps' in the business. 

Kelly, latterly Princess Grace of Monaco, was renowned for her glacial blonde beauty.

It helped her land starring roles in three of Alfred Hitchcock's most famous thrillers and win over Prince Rainier of Monaco, who made her his bride.

Altogether less regal was Kelly's behavior on her 1954 movie The County Girl, said Los Angeles-based Dorléac, who has enjoyed a long and illustrious career as a costume designer and who was nominated for an Oscar for the 1980 movie Somewhere in Time. 

'In 1978 while dressing renowned actor, John Williams, of Dial M for Murder and To Catch a Thief, for Battlestar Galactica in my Emmy winning costumes, he told me stories about Grace Kelley,' Dorléac wrote in an email to the Daily Mail. 

'She was commonly known as the “snob with round heels”, with Williams also telling me of Hitchcock’s ongoing sultry relationship with Kelly during the making of the films that they did together. 

'She ended up bedding four of the box office’s uppermost stars throughout The Country Girl's shoot,' said Dorléac, an author who is hoping to find a publisher for his new book of Hollywood gossip, Evocative Observations. 

The movie's four main actors were Bing Crosby, William Holden, Anthony Ross and Gene Reynolds. 

Kelly's affairs with Crosby and Holden are a matter of public record, but her alleged flings with Ross and Reynolds are not. 

Just two years after filming The County Girl, Kelly married Prince Rainier III and retired from the movie business. 

She moved to Monaco where she lived until her death in a car crash in 1982 aged just 52. 

Dorléac branded Kelly a 'sham' who used her 'physical beauty and pulchritudinous allure to get ahead' and suggested that both she and Prince Rainier cheated on one another. 

Hollywood doyenne Shelley Winters' sexual appetites were even more voracious than Kelly's - and she was far more brazen about sharing them, Dorléac said. 

'During a departure one evening from the downtown Music Center in Los Angeles, I happened upon a stranded screaming lady who was kicking the tires of a limousine that was parked close by, and realized it was Shelley Winters, damned over a flat tire,' he said.

'Listening to her cussing about missing an opening night after party I was headed for, I offered her a lift and had suggested she leave the driver with the car to take care of things.

'The excursion turned into a never-ending escapade of her many sexual conquests as we made our way towards Beverly Hills. A sort of guided tour of where she had banged, humped or sucked someone of renown and what exactly transpired.

'“See that crumbling duplex over there,” she whined, myopically looking to the right. “It’s where Errol Flynn ripped all my clothes off and made me sit on his face while pushing me to and fro. I had never done it like that before.” 

'She squinted once again, pointing a finger in front of me. “It was on the third floor of that brick building,” she screamed in my ear, “where Burt Lancaster bit me hard enough to cause blood on my nipples. 

'He was so pushy.'

Dorléac says Winters then regaled him with details of an extreme sexual encounter with Flynn that ended with The Adventures of Robin Hood star requiring stitches on an intimate body part.

Winters, an avowed Democrat, is also said to have pointed out where she and Marlon Brando had hooked up - and shared her one sexual boundary.

'"I never ever did anyone who was a Republican, except for Bill Holden,"' Dorléac says she confided.

Winters, who won two best actress Oscars, was married four times and died of a heart attack in 2006 at the age of 85.  

An equal-opportunities raconteur, Dorléac also detailed two Hollywood leading men known for being sex-crazed, both of whom suffered tragic and premature deaths.

The first was Dallas star Dack Rambo, who died of AIDS aged just 52 in 1994.

'Dack, whom I worked a full year on the TV series “The Sword of Justice“ was infamous for keeping the back door of his house unlocked until two o’clock in the morning to service all of his visitors,' Dorléac recalled. 

'Although he continuously tried to hide it by appearing in public with nubile blondes displaying a large set of knockers, he couldn’t keep it in his pants. 

'Sadly, his timing was responsible for his passing from AIDS that he developed several years later.

'He was forever trying to grope me during fittings, so I refused to see him unless there were tailors and my wardrobe assistants in the room. It became such a nuisance to confront him on the set or pass him on the street. He was such a leech.'

Rambo, whose real first name was Norman, was diagnosed HIV positive in 1991, retired from acting and came out as bisexual the same year, then spent the final three years of his life as an AIDS-awareness campaigner.

Making of a Male Model actor Jon-Erik Hexum had similar appetites for liaisons with men, despite being outwardly homophobic, according to Dorléac, who worked with Hexum on the ill-fated 1984 TV series Cover Up. 

'Although he was playing a hot fashion model, he was adamant about his costumes and would only wear plaid shirts, worn jeans with a red bandanna hanging out of his right back pocket like a Selma Avenue hustler, accompanied with a scowl while he disparaged and ridiculed other gay men,' Dorléac said. 

'The line of male visitors that stood outside his on set trailer was always long, waiting for their turn to be serviced. 

'It was hysterical to observe his motorhome bouncing about on its coil spring suspension system every hour of a twelve hour day. 

'Often, while placing his costumes inside the trailer during a break in the routine, I would walk in to find him in a compromising position groaning in ecstasy.'

Dorléac added: 'Additionally, there wasn’t anything one could tell him as he thought he knew everything.'

Tragically, that same precociousness was to bring about Hexum's shocking and untimely undoing.

In October 1984, Hexum was filming the seventh episode of Cover Up and 'trying to be cute,' according to Dorléac, who was on set that fateful day.

He pointed a stunt gun loaded with blanks at his temple and pulled its trigger 'for a laugh,' Dorléac explained.

But the blast from the muzzle of the weapon caused horrific head injuries to Hexum, who was declared brain dead six days later at the age of just 26.   

Dorléac continues to thrill readers of the Daily Mail with his 24 karat gold gossip about the great and the good of Hollywood.

Explaining his quest to expose the movie capital's secrets, he said: 'It’s always very difficult having to deal with such unbalanced, egocentric and difficult people the public are largely ignorant of. 

'They drool over their physical appearance and come to the conclusion that’s all that counts in judging talent.'