because no one has worked how to make them pay, and therefore there is no money to pay the professional journalist.

"If you think," he told the Guardian last week, "that free is going to produce something that's as much of a cost centre as good journalism - because it costs money to do good journalism - you're out of your mind."

The bad guys, he predicts, will be left to "gambol freely across the wastelands of an American city". That is because "the sad thing about contemporary journalism is that it actually matters very little". There could be no greater condemnation.

Simon, cultivating a style as gritty as his characters, takes it personally: he claims that the motivation for everything he writes is "revenge". His shows are revenge against those he holds responsible for the suffering and dysfunction of Baltimore, and revenge against the owners and craven editors who pulled the teeth of the watchdog.

A journalist portrayed in The Wire, billed as "a repellant police department toady", is named Marimow. One of the two Baltimore Sun editors he most blames for driving him from the newsroom was Bill Marimow. "I have," says Simon, "spent 10 years trying to get my revenge."

Simon made his name with The Corner, a mini-series docudrama which followed David Chase's groundbreaking The Sopranos onto HBO cable. It focused on a single corner in the black Baltimore ghetto where gangs of drug dealers bought and sold, fought and died. But it is an intimate portrait of a struggling community, rather than just another crime story.

That makes it a precursor of The Wire, which expands the portrait to the whole city, as seen from street level. It played on HBO from 2002 through 2008 and takes the form of a police procedural, but from a rebel point of view in which there are few heroes and no glamour. When HBO persuaded him to add the fifth, final, season he insisted that its theme would be journalism and its failures.

Simon wants his dramas to fill at least part of the gap left by those failures. He is now shooting the pilot for a new series for HBO set in post-Katrina New Orleans. He is focused on the hurricane-lashed but middle-class black community of Treme - pronounced "Trah-may" - which has been a seed-bed for New Orleans' musicians, and he plans to capture an "ornate" culture in a city as dysfunctional as any in America, but which has also produced the jazz which is "one of the most original things America ever invented".

There is a message. Simon is pointing out that the city's faith in its levees to protect it from flood was confounded, just as America's faith in its economy has been dashed. "It's a metaphor," he says, "for where we are in America right now."