In Canada, health warnings on cigarette packets are among the most direct and prominent in the world.

Big smile: Inside a smoker's mouth

The Canadian Government is in the process of introducing tough new regulations that would require tobacco manufacturers to display shock pictures, as well as information about diseases and how to quit smoking, on packets.

A Health Canada report found that there was a significant linear relationship between the size of the warning message and its influence on the decision to stop smoking.

"The larger the health warning message, the more effective it is at encouraging smokers to stop smoking," the report said.

"Larger health warning messages are more effective with those contemplating quitting and starting smoking - and least effective with hard-core smokers."

According to a World Health Organisation study in 1995, 83% of teenagers in Toronto recalled details of the Canadian warnings, compared to 6% of teenagers in Chicago who remembered details of American warnings.

Although the total number of smokers in Canada has dropped, the proportion of teenagers lighting up has risen from 23% in 1991 to 29% in 1996.

Australia bans tobacco advertising and most states ban tobacco companies from sponsoring sports events.

Global picture

1.1bn smokers Expected to be 1.6bn by 2025 Declining numbers in high-income countries Rising in middle- and low-income nations Smoking kills one in 10 world-wide By 2030, the proportion will be one in six -10m deaths a year (World Bank figures)

Since 1994, tobacco companies must include warnings such as "Smoking kills" and "Smoking causes lung cancer" on cigarette packs.

The warnings must cover 25% of the front of the pack, with health information on one-third of the back and toxic substance information on the side.

About one-third of smokers questioned in an Australian study said they had cut back on cigarettes after the stricter warnings were introduced.

In 1970, 41% of men and 29% of women in Australia smoked but had fallen to 27% and 23% respectively in 1995.

As of 1996 in Poland, warning labels covered 30% of the front and back of cigarette packs. Tar and nicotine levels must be listed.

Small warning labels are easy to ignore

A World Bank report released last year found that the warnings prompted some smokers to cut down or quit.

"Among Polish male smokers, 3% said they had quit following the introduction of the labels, an additional 16% said they had tried quitting, and a further 14% said they understood the health effects of smoking better because of the warnings."

The report said that to be effective, warning labels had to be large, prominent, and contain hard-hitting and specific factual information.