Lorillard Tobacco Co., the nation's fourth biggest cigarette maker, sued an anti-smoking group Tuesday over a radio ad that implies the company adds dog urine to its cigarettes.

The lawsuit filed in Wake County Superior Court claims American Legacy Foundation violated terms of the 1998 settlement between 46 states and the tobacco industry.

Under the settlement, the industry makes payments to the National Public Education Fund, which finances American Legacy's efforts to educate people about the dangers of smoking through advertising and other activities. It bars personal attacks on tobacco companies or employees.

American Legacy President Cheryl Heaton said in a statement that the company's ads have not been personal attacks and called the suit "meritless."

She said Lorillard is trying to crush "the largest and most important campaign ever launched to reduce youth smoking in the United States."

The organization filed a suit in Delaware last week to head off such a claim by Lorillard, arguing it is not subject to the terms of the $206 billion settlement because it didn't sign it.

Greensboro-based Lorillard said in its lawsuit that it tried to reach an informal agreement with American Legacy after the company began airing its "Dog Urine" radio ad last July.

In the ad, a person identifying himself as a dog walker phones Lorillard and tells the operator he wants to sell the company "quality dog urine" because it is "full of urea," one of the "chemicals you guys put into cigarettes."

Lorillard said it doesn't add urea to cigarettes, saying it is a substance found naturally in tobacco leaves.

"We strongly believe you can be edgy and their ads can be different, but you cannot and should not mislead the public with false attacks," Lorillard spokesman Steve Watson said.