Last month, CNN's average audience fell to 388,000, of which only 113,000 were adults in the 25-54 age bracket that advertisers covet.
And that decline is speeding up as the internet rises in popularity as a source for breaking news.
The figures also suggest CNN is losing viewers more quickly than rivals. For Fox, comparable figures (1.65 million and 319,000) are down just under 10 per cent annually. MSNBC (658,000 and 213,000) is falling by around 20 per cent.
"The biggest problem is inherent in their brand," says Robert Thompson, professor of television and popular culture at Syracuse University.
"They are trying to stick to old-fashioned, unbiased news broadcasting when their rivals have worked out that to draw an audience when there aren't major stories breaking you need to do the opposite."
CNN keeps a costly network of overseas bureaux and is still seen as the United States' most reliable TV news brand. It has resisted using partisan anchors. As a result, CNN remains a go-to destination only when major breaking news stories unfold. Last month was particularly tough because it was a quiet news month.
- Independent