David Simon, the journalist turned screenwriter of acclaimed drama series The Wire, today claimed that newspapers have fallen into decline because they do not value themselves highly enough.

The former Baltimore Sun reporter said newspapers had engineered their own downfall by giving away their stories for free online.

"I am worried about high-end journalism," Simon said during a Cannes seminar hosted by CNN's Piers Morgan.

"The disaster that happened to newspapers was that they didn't value their own content. They gave it away for free online.

"The difference with television is that we're now paying $67 a month to subscribe to a TV package. How can they charge that? Because they're investing in content. Journalism didn't do that; journalism didn't have that ambition."

Chat show host Morgan, the former editor of the Mirror, revealed that Twitter had become his "primary news source" and said he would give newspapers in print form "no more than 20 years" until they are extinct.

Morgan also claimed that a single tweet to his followers, who now number some 885,000, had added more than half a million viewers to an episode of his CNN chat show.

He claimed that his interview with Charlie Sheen, which almost never made it to air after the controversial actor turned up late, was swelled by an extra 500,000 viewers after Morgan tweeted about Sheen going AWOL moments before the programme started.