Three of Canada's tobacco giants began their defence Monday against a $27-billion class-action lawsuit in Montreal by calling a witness who said the dangers of smoking are no secret.

Historian and professor Jacques Lacoursière testified tobacco's health risks have been common knowledge for decades.

He pointed to over 700 references to the hazards of smoking dating back to the 1950s, including TV and radio reports, school manuals, government releases and health professionals.

One of the many examples included a newspaper article that outlined a significant increase in lung cancer risk following the prolonged use of cigarettes.

The proceedings will continue on Tuesday with the plaintiffs' cross-examination of Lacoursière.

"What these historians miss is all the coverage that came out in the media about how the industry was involved in a conspiracy to hide all that information," said François ​Damphousse , the Quebec director of the Non-Smoker's Rights Association.

"They knew about the health effects of their products, but they didn't meet the obligation to inform their public about what they knew."

Landmark class-action lawsuit

The complainants, two groups of individuals representing a total of 1.8 million Quebecers, allege three tobacco companies did everything possible to encourage addiction:

Imperial Tobacco.

JTI-MacDonald.

Rothmans, Benson & Hedges.

One group involves individuals who have become seriously ill from smoking, and members of the other group say they are unable to quit smoking.

They also allege the companies failed to properly warn their customers about the dangers of smoking, underestimated evidence relating to the harmful effects of tobacco, engaged in unscrupulous marketing and destroyed documents.

The class-action lawsuit, which is being touted as the biggest civil case in Canadian history, was first filed years ago.

Lawyers for the tobacco companies attempted to have the entire civil suit thrown out, but the judge rejected the dismissal.