Canada's three main tobacco companies are set to do battle in a Montreal court today in the biggest civil case in Canadian history.

A group of Quebec smokers is suing Imperial Tobacco Canada, Rothmans, Benson & Hedges and JTI-Macdonald.

They claim 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.

It's the first time tobacco companies have gone to trial in a civil suit in Canada, and up to $27 billion in damages and penalties are at stake.

The tobacco companies say they vehemently deny the allegations.

On another front, six provinces are teaming up to sue Canadian tobacco firms for health-care costs.

B.C., New Brunswick, Nova Scotia, Saskatchewan, Manitoba and P.E.I. are retaining a national legal team to help them prosecute Canadian tobacco companies.

They're seeking to recover billions of dollars.