Rupert Murdoch's News Corp posted its biggest ever quarterly net loss, after taking an $8.4 billion writedown for the value of its Dow Jones acquisition, broadcasting licenses and other assets.

Excluding the charge, the results missed Wall Street forecasts as the recession exacerbated the fall in newspaper advertising sales and hit the company's other properties.

News Corp shares fell 6.3% to $6.50 in after-hours trading and have shed about 65% of their value in the past 12 months.

"It is the worst global economic crisis since News Corp was formed 50 years ago," Murdoch, chairman and chief executive, said on a conference call with analysts.

He said it was impossible to be completely prepared for such a harsh economic downturn, but News Corp is cutting costs and staff where appropriate, as it expects advertising-supported businesses to weaken more.

Its Fox businesses have cut about 800 jobs, while its Wall Street Journal, which has seen ad revenue fall 20%, said it had eliminated 25 journalist jobs. The company also has slashed $100 million in costs at Dow Jones, though it said there were no plans for layoffs at Dow Jones Newswires.

The latest media company to report gloomy results as advertisers slash their budgets in the weak economy, News Corp said its net loss was $6.41 billion, or $2.45 a share, for the fiscal second quarter ended December 31. That compared with a profit of $832 million, or 27 cents a share, a year earlier.

News Corp wrote down $3.6 billion in goodwill, much of which is likely because of Dow Jones. Murdoch bought Dow Jones for $5.6 billion in 2007, a 65% premium to its then market value.

It wrote down $4.6 billion in broadcast licenses from the U.S. Federal Communications Commission and $185 million in newspaper assets, which include the New York Post.

News Corp also owns the Fox television network, 20th Century Fox movie studio, the MySpace online social network, satellite TV network Sky Italia, and newspapers throughout the United States, Britain and Australia.

Excluding the impairment charge, News Corp's December quarter profit was 12 cents per share, lower than the average analyst forecast of 19 cents, according to Reuters Estimates.

Revenue fell 8.4 percent to $7.87 billion, also below the average Wall Street forecast of $8.35 billion.

Operating profit fell at nearly every division of News Corp, from filmed entertainment to local television, newspapers, books and information services.

"The big thing that really is killing us is a lack of automobile advertising," Murdoch said.

Fox Interactive Media posted an operating loss of $38 million, in part due to the launch of MySpace Music.

One bright spot was cable network, whose operating profit rose 27% to $428 million on strength at the Fox News Channel, the Big Ten Network and Fox International Channels.

As expected, News Corp cut its fiscal 2009 operating income forecast to a decline of 30% versus its previous forecast for a fall in the mid-teen percentage. Murdoch forecast full-year operating income of $3.5 billion.

The outlook assumes that advertising or economic conditions do not worsen, News Corp said.