Ministers have unveiled details of plans to ban smoking in pubs serving food, restaurants and other enclosed public places, including bus stops.
The government is starting its consultation on a smoking ban
But Health Minister Caroline Flint denied an outright ban in all public places in England was planned.
She said she wanted smoking banned in workplaces by the end of 2007 and in pubs where food was served by 2008.
Critics said the plans did not go far enough, while smokers' lobby group Forest said they were "unnecessary".
Ministers are inviting views from the public, charities and businesses on the proposals.
Ms Flint said there would be some exemptions, for example pubs not preparing and serving food.
Some of the issues that will be considered in the 11-week consultation include whether, for example, pub gardens would be included, and what sort of penalties would be implemented to enforce the ban.
It also seeks to define what an enclosed public space is - with bus shelters, football stadiums and railway stations all likely to be included.
It is also suggested that smoking be banned within one metre of the bar in pubs where smoking is allowed.
The consultation paper puts forward details on the general policy outlined in last year's Choosing Health: Making Healthy Choices Easier White Paper.
Key consultation areas
Definition of enclosed public place/workplace
Definition of prepare and serve food
Offences, penalties and defences
Timetable for a ban
Enforcing a ban
Critics want England to follow the Republic of Ireland's blanket ban on smoking in all pubs and bars.
Scotland is also planning a comprehensive ban expected to be introduced next year.
The Welsh Assembly will be provided with powers so they can reach their own conclusion about what to do about smoking.
The plans suggest institutions such as prisons, residential care and mental health hospitals should not be covered by a ban.
Critics, who have been led by medical groups and the anti-smoking organisation Action on Smoking and Health (Ash), said the proposals did not go far enough.
They argue that the more exemptions there are, the more confusing and unenforceable the ban will be.
Lib Dem health spokesman Steve Webb accused ministers of holding back from a complete ban in enclosed public spaces becauses they feared it would be unpopular.
"If the government are going to stop passive smoking because it is bad for you, then whether you are eating or not is irrelevant."
For the Conservatives, shadow health secretary Andrew Lansley said the plans were "unsustainable".
"We should give the industry and businesses the opportunity to make further and faster progress with a voluntary code," he said.
"If this is not achieved, then there should be legislation to ensure every one who wishes has access to a smoke free environment and enclosed public places are smoke free."
Professor Alex Markham, Cancer Research UK's chief executive, said: "We believe that public support for fully comprehensive smoke-free legislation is stronger than ever, and the government's consultation is an ideal opportunity for people to make their views known."
The British Medical Association's deputy chairman Dr Sam Everington said: "Given it is acknowledged that second-hand smoke kills, the lives and health of employees must be the priority. It should not matter where an employee works."
But smokers' lobby group Forest is launching an advertising campaign to persuade the government to reject the smoking ban.
Forest director Simon Clark said: "Punitive legislation is unwelcome and unnecessary and would infringe the rights of hundreds of thousands of people, including publicans and restaurateurs."