Major tobacco companies say the U.S. government has gone too far with the new warning labels it is requiring them to attach to every pack of cigarette, and they're fighting back.

The U.S. Food and Drug Administration's latest demand is for graphic labels that include a picture of a sewn-up corpse and sickly-looking diseased lungs with the bleak warning: "Smoking can kill you" and "Cigarettes cause fatal lung disease."

And the labels must take up the entire top half of both sides of every pack of cigarettes, amounting to 20 per cent of the entire packaging, according to the new FDA rules.

The cigarette companies -- four of the five largest in the U.S. are involved in the suit -- say the warnings violate their right to free speech, and are excessively punitive.

"Never before in the United States have producers of a lawful product been required to use their own packaging and advertising to convey an emotionally-charged government message urging adult consumers to shun their products," the suit states.

The action was filed in a federal court in Washington on Tuesday.

The companies also say the new requirements will cost them millions to implement and go well beyond simply stating a message about the adverse health effects of smoking.

It isn't fair, the suit alleged, that the government is now forcing the companies to feature government anti-smoking advocacy more prominently than their own branding.

R.J. Reynolds Tobacco Co., Lorillard Tobacco Co., Commonwealth Brands Inc., Liggett Group LLC and Santa Fe Natural Tobacco Company Inc. are all involved in the suit.

The owners of Philip Morris USA, the largest cigarette maker in the U.S., are not involved in the suit.

The sewn-up corpse and diseased lung are just two of nine warning labels that tobacco companies will be required to print on their packaging, along with the dire warnings and a phone number for a stop-smoking hotline.

They were defended in June as frank and honest warnings about the dangers of smoking by U.S. Health and Human Services Secretary Kathleen Sebelius.

The tobacco makers complain the warning labels are unnecessarily emotional, and the photos have been manipulated to emphasize the government's point. They claim the 'corpse' with its chest apparently sewn up is actually an actor, and the image of the yellow and black lung looks worse because the so-called healthy lung has been cleaned up to enhance the contrast.

The FDA has not commented publicly on the lawsuit as it is pending litigation.

Canada's requirements for tobacco companies are more strident than those in the U.S. Under current laws, cigarette packages are required to have a health warning that takes up 50 per cent of both the back and front of the package, in both French and English.

They must also include a warning label on the inside of the package, and must avoid the use of the terms "light" and "mild" from their packaging.

In addition, the amount of tar, nicotine, carbon monoxide, formaldehyde, hydrogen cyanide and benzene emission must be clearly listed on the package.