Its popularity was so great that its creator, Shonda Rhimes, found herself first voicing surprise.

Before long, however, the carping started and instead she was defending the show.

The success of Grey's Anatomy comes at a cost . . . namely, the 24/7 monitoring of its cast of increasingly famous actors.

Into that parallel universe of celebrity obsession has exploded a most unflattering controversy that has tweaked two of America's most sensitive nerves: race and the treatment of gays. It is a row which earlier this month led to the firing of one of the show's principal actors, who is now pondering a lawsuit against ABC and its parent, the Walt Disney Company.

Despite the show's runaway success, audiences became deeply polarised over the ever more inappropriate antics of individual characters, such as Meredith sleeping with her depressed best friend, cuddly George O'Malley (played by TR Knight) when he is spurned by the real object of his affections, and then ignoring him the moment the naughty deed was done.

"Things like that were planned from the beginning, " said Rhimes, attempting to defuse the disgust of some viewers over Dr Grey's on-screen behaviour. "People want there to be real characters on TV, yet when there actually is a real character who's flawed, it's hard to take."

That some of her cast members would eventually begin to display unfortunate flaws of their own was not something that Rhimes was prepared for, however. Life for her would certainly have proved a lot easier, for example, if Washington had not got into a flaming row on set last October with fellow cast member Patrick Dempsey.

Certainly, it would have been better if in the course of that squabble, Washington had not uttered a gay slur directed at Knight.

The word, uttered apparently in a moment of high passion, was "faggot". Gays can use it without risk when talking about themselves, but in America it is extremely offensive if it is a straight man talking.

When this unfortunate exchange became publicly known at the start of this year, a giant fuss inevitably ensued that should have had a headline shelf-life of just a few days. A few days later Knight confirmed for the first time that he was homosexual.

During a backstage press conference at the end of the Golden Globes ceremony, the endless questions about the incident led Washington to defend himself and, in the process, utter the same word all over again.

To say it once was careless, but twice? Well, it was professional hara-kiri.

Washington, at the urging of ABC and surely also of his agent did his best to show public remorse: he made the rounds of talk shows saying he didn't have a bigoted bone in his body; signed on to counselling to make sure that if there were such a bone it was removed for good; and even agreed to record a public service announcement for broadcast on the network reminding people that insulting gay people is not a good thing.

But then, with shooting in summer hiatus, Washington took a weepy phone call from Rhimes earlier this month in which she told him that his services for season four (and any thereafter) would not be required. A good nine months after his altercation with Dempsey, he was being dumped.

Cue a nationwide debate about the rights and wrongs of the dismissal. Gay activists seem pleased, but not all of them. Leading black spokesmen are troubled by the move, but they are not in consensus either. Most enraged is Washington himself, who has dedicated recent days to putting out what he says is his side of the story.

The gyst of his contention is that ABC has sacked the wrong man. It is Knight who should be looking for new work, not him.

According to Washington, the trouble can be traced to Knight who, he alleges, had been going around bad-mouthing Dempsey to him (notably in the course of a two-hour plane journey) and others on the Anatomy set. In his subsequent confrontation with Dempsey, Washington used the f-word but did not direct it at Knight. To say otherwise, he insists, is "a lie". He goes on to accuse Knight of deliberately conspiring thereafter to exaggerate the significance of his using the slur in an attempt to gain leverage with the producers and thus win greater air-play for his character and also a higher salary.

Washington's spokesman, Howard Bragman, has noted that the actor has done everything he was asked to by the network to put out the original fire.

"If they wanted to fire him why didn't they fire him when it happened? Why did they say, 'Here's what you need to do if you want to come back. . .' and then, when he did everything that was asked of him, he still gets fired. Why do you treat somebody like that?"

Tavis Smiley, a respected black radio and television broadcaster, offers the view that the actor's anti-gay expletive was always going to bring him down. "As a society we are still grappling with the notion of forgiveness and redemption, " Mr Smiley said. "What this incident shows us. . . is there is some pain so deep, that an apology, no matter how sincere, just doesn't suffice."

The gay rights lobbyist Neil Giuliano contends that Washington has fallen foul of a new mood in America where slurs against minorities are no longer easily forgiven. He noted the hot water that the right-wing commentator Ann Coulter found herself in after she applied the faggot word to Democratic presidential hopeful John Edwards.

"All of this is crescendo-ing, with people saying, 'Enough is enough', " he said.

The more Washington says on the subject the deeper his hole seems to get. The irony is that Grey's Anatomy has found success precisely, as Rhimes concedes, because its characters routinely make more errors of judgement than there are blades in a surgeon's scalpel set. But in the real world of politically correct America, her actors can make no such errors. Washington delivered a line with one offensive word in it and he is off the ward for good.

THE BEST MEDICAL DRAMAS EVER DR KILDARE (1961 . . . 1971) A young Richard Chamberlain starred and got many the female pulse racing.

M*A*S*H (1971 . . . 1983) Fact! The finale of this black comi-drama, set in Korea was the most watched episode in US television history . . . well, so Wikipedia says.

St Elsewhere (1982 . . . 1988) Hard-hitting realism from the same team responsible for 'Hill Street Blues' ER (1994 . . . present day) The glory days were the Anthony Edwards/George Clooney/Julianna Margulies/Noah Wyle ones.

It's still good though.

Nip/Tuck (2003 . . . present) Oh so trashy but tremendous fun. Bizarrely, Julian McDonald who plays surgeon Christian Troy, used to be married to Danni Minogue House (2004 . . . present) Hugh Laurie does a star turn as medical genius Gregory House, only to become a surprise sex symbol in the US.