Banning smoking in prisons would cause "disorder" and an increase in assaults on staff, the head of the prison service has warned.
The government wants to ban smoking in enclosed spaces
Phil Wheatley said about 80% of prisoners smoked and a total ban would only "drive it underground".
Prisoners should be allowed to smoke in their cells but it should be banned in other indoor areas, he told MPs.
The government wants to ban smoking in all enclosed public spaces in England, except clubs, and food-free pubs.
The proposed legislation is designed to protect workers from the effects of second hand smoke.
But Mr Wheatley said a total ban in prisons would put staff at risk from physical assault.
"I would expect to find there was an increase in incidents of assaults on staff, that we ended up with prisoners who were more likely to be troublesome and an increased risk of disorder," he told the Commons health select committee.
There was also a question of prisoners' welfare, he added.
"We do need to make sure we do not cause significant problems for disturbed people arriving with us with already a multitude of problems, many of them coming off drugs, many of them with serious alcohol problems and many of them potentially suicidal.
"As we try to settle them into prisons I don't want to keep any more pressure on them than I need, in the interests of keeping people alive and safe."
He said he wanted to see smoking by staff and prisoners restricted to outdoor areas - but he said prisoners should be allowed to smoke in their cells.
He said the prison service would work towards putting smokers and non-smokers in separate cells, even though this would "slightly reduce" the number of prisoners it could accomodate.
He also warned about the cost of weaning prisoners off cigarettes, which he said worked out at £158 per inmate for nicotine replacement therapy.
And he stressed a total ban would also increase smuggling and make tobacco - traditionally used by inmates as an alternative to money - "more available as a currency than it is".
It would also create "control problems in some establishments", he added.
"You don't have a lot going for you in prison. You are deprived of most of things you might ordinarily enjoy... to take yet another thing away will not be wildly popular with a group who are not always charming and pleasant in their behaviour."
There would be particular problems in higher security prisons, "where taking things off prisoners who are doing very long sentences always carries a degree of risk".
He added: "We would not ever achieve complete success unless we put lids on prisons."
Asked if he was concerned about non-smoking prisoners locked up with smokers launching legal action under human rights legislation, Mr Wheatley said: "There is always a risk of a variety of legal actions being brought against us and this might well be another one."
Asked why prisoners were not also allowed alcohol, he said: "We don't give access to anything that is a mind-altering substance."