Three of Britain’s Oscar-nominated screenwriters say that an increasing tendency among film studio bosses and directors to “mutilate” film scripts is forcing top writers to either direct their own work or write for television, where they command greater respect.

Jeffrey Caine, William Nicholson and Steven Knight – whose acclaimed screenplays include those for The Constant Gardener, Gladiator and Dirty Pretty Things respectively – told the Observer that writers were often sacked without warning from the studios and would then discover that their original work has been altered beyond recognition by a production line of writers.

Caine said that studio executives, directors or actors who “ride roughshod” over film scripts can leave writers feeling embarrassed when their names appear in the credits. Writers often find themselves blamed for excruciating dialogue they never wrote, he said, adding: “I have seen lines of dialogue in films with my name on them that I wouldn’t have written under torture.”

To add insult to injury, writers are sometimes unceremoniously removed from projects, though their name may appear in the credits. They may not even be told they have been replaced: they discover their sacking by chance on a blog or trade report. Nicholson recalled delivering a commissioned screenplay and receiving a phone call from the studio saying it was “wonderful – we’re so excited”. He then heard nothing. Two years later it appeared in cinemas; other writers had taken it on. His name was on it, but it bore little relation to his original.

The phenomenon is not new. Howard Clewes, a leading British screenwriter, took his name off Mutiny on the Bounty, starring Marlon Brando, in 1962, because he was so dismayed by the rewrites. Today’s writers do not have that option. Writers’ Guild rules do not permit writers to take their name off a screenplay if they have been paid more than a certain amount. Studios can, in effect, buy their names.

Nicholson said he understood the pressures on studios, particularly with huge financial investments, but lamented “a failure of manners”. They could, he said, send “even an email, saying they appreciate ‘you gave six months of your life, but … we’ve moved on’. They never, ever, do.” He added: “Although I understand why they treat writers so badly, it’s not in their interests to do so. They will get poorer work from their writers. Create an atmosphere of trust and [writers] will take risks and write better for you. Create an atmosphere of fear and neglect and they won’t.”

Nicholson won an Oscar nomination for Shadowlands in 1993, starring Anthony Hopkins, which he said was shot from his screenplay because Richard Attenborough was both a great director and a gent who respected a script. But on Gladiator he was the third writer – “two other writers … had suffered the ignominious fate, which I have suffered many times”. TV was “very significant” for top writers, he said, because there they have “enormously more power and respect than film writers”.

Caine’s screenplay for The Constant Gardener, starring Ralph Fiennes, was his adaptation of John le Carré’s noveland showered with nominations for Oscar, Bafta and Writers’ Guild of America awards. It was filmed largely as he intended – a rare thing in the industry, he lamented. Film-makers who do not understand the subtleties of storyline, characterisation and dialogue are “only interested in the crudest storytelling, and the most banal and superficial elements of character”, Caine said. “The writer tries to put in subtleties, but they sometimes end up being excised from the script.”

He likened the problem to a chef being asked to prepare his signature dish for a dinner and finding the host smothering the meal with ketchup. “Many major big-budget movies these days taste of ketchup,” he said, because each change to the original dilutes it. “All the best stuff that made it cohere and made it work is no longer there, and all you’re left with is pretty pictures … That’s why so many blockbuster, mass market films are so bland.”

The problem applies less to independent films and more to originals than adaptations as with the latter there is a basic storyline and also characterisations producers and the director know they can’t stray from too far.

Hollywood’s principle on mass-market movies is the more writers the better. Observing that some of the best screenplays came from writer-directors such as John Huston and Billy Wilder, Caine said that DIY directing or producing is now the best way to preserve the integrity of screenplays, though he has no wish to pursue that route himself. But writers doing so include Richard Linklater, whose Boyhood is an Oscar frontrunner, and Damien Chazelle, who wrote the acclaimed thriller Whiplash.

Ultimately, decisions are driven by money, Knight said. “With a film … it costs a lot of money to get it made. They’re terrified they’re going to lose that money. They look at what’s worked before and think ‘we’ll do that again because that worked’. Therefore, they will take a script they like – and then change it so it resembles something else because they think that’s engineering it towards success, which isn’t the case.”He feels that television is now the “home of really good writing” because writers are left alone and directors shoot what’s on the page.

Although this is not a new phenomenon. But, in a way, film-making was ever thus. Caine claims: “Cinema is the greatest artform ever devised. Had Shakespeare lived now, imagine what he could have done. Then imagine the mutilation. He would no doubt have been a writer-director, as he actually was.”

Directing his comments at audiences and critics, he added: “Before you rush to blame the screenwriter for a bad script, just remember that it may not be the script that these guys signed off on.”