Smoking could be banned in bus shelters and sports stadiums in England, the government has suggested.
The ban is due to come into force next summer
Health Minister Lord Warner said new laws to ban smoking in enclosed public spaces would give the government powers to prevent smoking in bus shelters.
But the powers could only be used where there was "significant risk" people would be exposed to "significant quantities of smoke".
Critics of the ban say ministers are trying to stop smoking in the open air.
As the House of Lords debated the Health Bill, Lord Warner said it included powers which might be used to ban smoking in "sports stadiums, bus shelters and entrances to public buildings or workplaces".
But the government watered down the powers by amending the bill to cover only areas with significant amounts of smoke.
The Health Bill is still going through Parliament. If it is passed, the ban is due to come into force in summer 2007.
Simon Clark, director of smokers' lobby group Forest, said: "It shows breathtaking arrogance on behalf of the government that they can be talking about banning smoking outdoors even before an indoor smoking ban has been enacted or introduced.
"It suggests that the public, MPs, and peers have been hoodwinked into believing that a smoking ban was being introduced to protect workers from the effects of passive smoking in public places.
"Clearly if the government decides to ban smoking outdoors as well, this has nothing to do with passive smoking and everything to do with forcing people to give up, which is a blatant form of social engineering."
But a spokesman for anti-smoking charity Ash said it did not think the government intended to cover sports stadiums and similar public places against the risk of second-hand smoke.
"This is something we will be arguing for if the act comes into force and over the next few years," said the spokesman.