Smoking in enclosed public places will be banned in England from 1 July next year, the government has announced.
The government says 600,000 people will quit as a result
The ban covers virtually all enclosed public places including offices, factories, pubs and bars, but not outdoors or in private homes.
It follows similar bans in the Irish Republic and Scotland - a ban in Wales starts on 2 April.
Ministers say it will protect everyone from passive smoking, but opponents say the total ban is "draconian".
From 1 July pubs and restaurants will have to display prominent "no smoking" signs around their premises.
Health Secretary Patricia Hewitt said the ban was a "huge step forward" which would save thousands of people's lives.
The cost of implementing the ban has been estimated at about £50m.
Ms Hewitt said the ban would protect everyone from second-hand smoke, while making it easier for smokers to quit.
"The scientific and medical evidence is clear - second-hand smoke kills, causing a range of serious medical conditions including lung cancer, heart disease, and sudden infant death syndrome," she said.
"This legislation will help to prevent the unnecessary deaths caused every year from second-hand smoke, and recognises that there is absolutely no safe level of exposure."
Irish Republic: March 2004
Scotland: March 2006
Northern Ireland: April 2007
Wales: April 2007
England: July 2007
The government predicts about 600,000 people will give up smoking as a result of the law change.
The news was welcomed by health campaigners. Dame Helena Shovelton, chief executive of the British Lung Foundation, said: "This is a victory for all those of us who have campaigned so vigorously to improve public health."
She said it would reduce the death toll linked to smoking and that tens of thousands of people with lung disease would once again be able to visit pubs and restaurants.
Cancer Research UK chief, Prof Alex Markham, said 1 July would be an "historic day".
"Making workplaces and enclosed public places smoke free will bring about some of the most significant health improvements the country has seen in decades," he said.
British Beer and Pub Association boss, Rob Hayward, welcomed the announcement, saying it gave businesses "greater clarity" and would allow them to prepare their customers for the changes.
The Cabinet originally proposed prohibiting smoking only in pubs serving food, in line with Labour's election manifesto - but MPs eventually backed a total ban in enclosed public spaces in a free vote.
Simon Clark, director of the smokers' lobby group Forest, said that decision had been "draconian".
"From July next year it will not only be illegal to smoke in every pub, club and bar in the country, it will also be impossible to set up a private club run by smokers for smokers," he said.
"That's an amazing state of affairs but typical of a government that seems determined to interfere in every aspect of our daily lives."
The health secretary is also launching a Smokefree England campaign, to advise England's 3.7m businesses to prepare for the ban.