Four major U.S. tobacco companies are suing the federal government, saying that forcing them to put graphic warning labels on cigarette packages is unconstitutional.

The companies say the new rules violate their right to free speech.

An attorney representing Lorillard Tobacco Co. says the government can engage in all the anti-smoking advocacy it wants in whatever language and pictures it chooses. But he said it cannot force those who lawfully sell tobacco to carry its message.

The U.S. Food and Drug Administration has not commented on the lawsuit.

The FDA announced in June a series of rotating warning labels for cigarette packs, including such graphic pictures as a corpse in his coffin, a pair of diseased lungs, and a mouthful of rotten teeth. The new labels are to start appearing next year.

Government health officials say the new labels are much more honest about the dangers of cigarettes than simple printed warnings.