NEW YORK - Longtime CNN host Lou Dobbs shocked his viewers last night by announcing that he would be leaving the network effective immediately.

The daily host of "Lou Dobbs Tonight" addressed his viewers after giving the day's headlines and told them that last night's show would be his final time in the anchor chair.

He said that CNN had let him out of his contract early and that he was considering a number of options for the next stage in his career.

"I will let you know when I set my course," he said. He said he wanted to "contribute positively to a better understanding of the great issues of our day."

CNN President Jon Klein in a statement hailed Dobbs' "appetite for big ideas, the megawatt smile and larger than life presence he brought to our newsroom."

"With characteristic forthrightness, Lou has now decided to carry the banner of advocacy journalism elsewhere," Klein said. "We respect his decision."

The longest-running anchor on CNN's air, Dobbs was one of the nation's leading financial journalists before turning his program in a more opinionated direction. His persistent advocacy against illegal immigration angered many.

"I'm the last of the original anchors here on CNN and I'm proud to have had the privilege of helping to built the world's first news network," he said.

CNN's average prime-time audience was third behind Fox and MSNBC during October, and it was even eclipsed by sister network HLN among younger viewers, according to the Nielsen Co.

Dobbs has written three best-selling books: "Independents Day: Awakening the American Spirit" in 2007, "War on the Middle Class" in 2006, and "Exporting America" in 2004.