Tobacco firm Philip Morris Europe, makers of brands such as Marlboro, disagrees, said it could accept warnings that are up to around 15% of pack sizes.
A directive, which goes before the European Parliament in Strasbourg on Wednesday, would also mean massive increases in the size of health warnings and descriptions like "low tar" and "mild" being banned.
Some MEPs have proposed an amendment to the directive requiring graphic photos, including tar-stained teeth, to be added to packs.
"If vivid pictures of rotting teeth and blackened lungs bring home the true cost of smoking, print them on packs in the UK in full colour," said Labour MEP and Health Spokeswoman, Catherine Stihler.
But the proposal is opposed by EU Health and Consumer Protection Commissioner David Byrne.
Warnings
Messages could say: "Smoking kills half-a-million people each year in the European Union" or "Smoking causes impotence".
At present, EU member states ask for health warnings to cover at least 4% of the pack.
"I admit it will make the packs ugly," said Dutch Liberal MEP and smoker Jules Maaten.
"But it will also make the text readable... and we are quite sure it allows enough space for any brand to still market itself."
Tobacco firm Philip Morris Europe, makers of brands such as Marlboro, disagrees, said it could accept warnings that are up to around 15% of pack sizes.
Denise Claveloux, corporate affairs director for Philip Morris Europe, said: "What we're looking for is balance. I'm not sure we're achieving balance with the kinds of numbers that are being suggested."
Even if the tobacco directive is agreed in the European Parliament, it will still have to be approved by EU member governments.
Canada has already made health warnings compulsory on 90% of the surface of a cigarette pack and is expected to introduce shock pictures on packets by the end of the year.
The British Medical Association (BMA) has joined forces with its counterparts in the other 14 EU states to appeal to the MEPs to vote through the tough measures.
Dr Mac Armstrong, BMA Secretary, said: "The proposals offer an unparalleled opportunity to protect Europeans from a uniquely harmful product."
The British Dental Association (BDA) also backs the proposals for strengthening warnings on cigarette packets.
A spokeswoman said: "The BDA would like these warnings include damages that smoking can cause to teeth and gums
"Healthy teeth need healthy gums but gums can be seriously harmed if you smoke. The risk of oral cancer is also greater in those who smoke."