The head of news network CNN says he is quitting his post.

Jim Walton said the company needs new leadership at a time its flagship US network is suffering through some of its poorest ratings ever.

He has held the position of president of CNN Worldwide for the past 10 years.

But the network is in 3rd place behind US rivals Fox News and MSNBC in prime time slots.

He said he will continue working until the end of the year while the company looks for a successor.

The 54-year-old began working at CNN in 1981 shortly after it started.