Eighty-six per cent of fathers who smoke continue to do so at home even when their child has been in hospital, a study has found.
Men in the study did not listen to their wives' advice
Just over half smoked in front of their child, the University of Hong Kong research discovered.
Most women knew their husband's habits should alter, but family tensions stopped them pressing for change, the Journal of Advanced Nursing reported.
Forest, the smokers' rights group, said bans would increase smoking at home.
Researchers surveyed the mothers of 1,483 children, with an average age of five, admitted to four major hospitals in Hong Kong.
None of the mothers, who were mainly housewives, smoked, but all of the children's fathers, who worked in factories, crafts, services and shops, did.
Half of the children suffered from respiratory problems - putting them at high-risk from passive smoking - and 60% of the children had been admitted to hospital more than once.
The researchers offered half of the mothers health advice, booklets and no-smoking stickers and weekly telephone reminders.
The other mothers received no advice or reminders.
The families were followed for a year after the initial contact.
At three months, more mothers in the education group moved their child away from the father's smoke - but there was no difference between the groups after 12 months, when just over half of women in both groups said they removed children from the smoky area.
Smoking ban fears
Dr Sophia Chan, who led the study, said: "When we spoke to the mothers, some of them expressed concerns about the conflicts that had arisen when they had asked their husbands to quit smoking and they said that they preferred to take evasive action instead.
"Although we found our initiative had some short-term benefits, many of the mothers found it difficult to persuade their husbands to quit smoking and the education group were more likely to take evasive action, such as moving the child out of the room.
"With an increasing number of countries worldwide introducing smoking bans in public areas such as bars and restaurants, there are fears that more parents will smoke at home and that this will have an even greater effect on children."
Amanda Sandford, of the group Action on Smoking and Health, said there were cultural differences between the UK and Hong Kong.
But she added: "One thing is universal. Children shouldn't be exposed to second hand smoke and deserve protection.
"The ideal is for parents to stop altogether. But the important thing is to ensure that children are not exposed to second-hand smoke."
Simon Clark, director of the smokers' lobby group Forest, said parents of a child with asthma would be advised to avoid smoking in a small enclosed room when their child is present, but there was no reason for them to give up completely?"
He added: "Ironically, one of the many downsides of a total public smoking ban is that people are more likely to smoke at home instead of in a well-ventilated bar or restaurant surrounded by adults who have chosen to be there.
"The anti-smoking lobby is now targeting parents who smoke at home. The idea, clearly, is to make them feel guilty about their habit by implying they are harming their children. It's a form of moral blackmail."