Bar operators have criticised the Ombudsman's suggestion for them to be made criminally liable if any smokers light up inside their venues.
The Hong Kong Bar and Club Association said on Friday that such a move would be unreasonable and impractical, and businesses already do their best to encourage customers not to break the law.
The association's spokeswoman Angie Chak said it is impossible for staff to keep an eye on every customer.
"They are not supposed to check everyone, because they are very busy," Chak said.
Meanwhile, the head of the Tobacco Control Office, Jeff Lee, said his staff had already stepped up efforts to tackle smoking in prohibited areas before the Ombudsman accused them this week of doing too little.
Lee said 20 retired police officers were recently brought in to help catch offenders.
But he also said he accepts the watchdog's findings, and enforcement will be stepped up further.