Pubs and restaurants fear that the ambiguity surrounding next year's smoking laws mean they won't be able to adapt their premises in time for the ban.
Among other proposals, the three-month consultation paper launched on Monday suggested smokers could light up only in areas where 50% of the walled area is open to the outdoors.
But operators are concerned that by the time final decisions have been made, which some warn could be as late as March 2007, the transition period before next summer's deadline will be too tight.
Café Lazeez chief executive Zahid Kasim said he needed more time at his three restaurants. "I can't see how we will suddenly be ready. It's a very short period to adapt to such a major change."
Derek Andrew, managing director of 543-strong Wolverhampton & Dudley Breweries' managed Pathfinder division, called the timing "characteristically late in the day".
"We've had to work on assumptions and hopefully the 50% rule won't be a problem," he added.
According to a spokesman for the Association of Licensed Multiple Retailers, operators are wary of making final business decisions because the bill has already changed dramatically.
Punch Taverns chief operating officer Adrian Fawcett said he was disappointed at the "lack of detail in terms of when it will become law".
British Beer and Pub Association chief executive Rob Hayward called for a timetable "to ensure a smooth and surprise-free implementation".
Under the plans, smoke-free premises will have to display "no smoking" signs no smaller than A5 in size and owners face fines of up to £2,500 if customers are caught lighting up.
- Smoking areas: 50% of walled area must be open to outdoors
- Signage: "Prominent position" and A5 minimum size
- Fine: £2,500 max
- Exemptions: Sports stadiums and designated rooms in: hotels, mental health units, prisons and oil rigs
By Tom Bill