A complete ban on smoking in prisons in England and Wales is to be phased in from January, despite warnings from prison governors that it risked making jails more unstable.

The decision follows a seven-year battle by prison unions to include jails within the ban on smoking in public places introduced in 2007. It spells the end of the “tobacco barons” operating inside the jails and finally ends the day when “snout” was the traditional currency behind bars.

More than four in five prisoners smoke, and while smoking in communal areas has been banned for some time, prisoners have been allowed to smoke in their cells.

The decision to roll-out the complete ban on smoking in jails coincides with the findings of air-quality tests undertaken in six prisons. The results showed that staff were spending at least one-sixth of their time breathing in secondhand smoke levels higher than World Health Organisation guidance limits. The secondhand smoke was a significant health hazard to prisoners and staff, the results showed.

The announcement also follows legal challenges over the health risks of passive smoking resulting from the failure to apply the smoke-free legislation to the whole prison.

The ban will take effect in all prisons in Wales from January and in four prisons in south-west England – Exeter, Channings Wood, Dartmoor and Erlestoke – from March.

Smoking will be banned in the interior of open prisons from next month, but will be allowed outdoors. Plans are also under way to provide voluntary smoke-free areas in prisons from early next year.

The selective, phased introduction of the ban is believed to be because of concerns about its impact on an already volatile prison population. Andrew Selous, the prisons minister, said implementing smoke-free prisons was a “difficult thing to do” given the high prevalence of smoking and the “unique environment” of prisons, but the ban was necessary because of the UK’s smoking legislation and health reasons.

“We have no plans to move to smoke-free prisons overnight and will only do so in a phased way that takes into account operational resilience and readiness of each prison,” he said. “The operational safety and security of our prisons will always be our top priority.”

The prisons minister said the smoking ban would eventually apply to all 136 jails in England and Wales. “From now until the smoke-free implementation date, the first prisons will be encouraging and supporting prisoners to stop smoking through a range of smoking cessation support and advice, including nicotine replacement therapy,” he said.

“We will continue to take a sensible and considered approach, using the experience of the first prisons to go smoke free to inform the speed at which we move to smoke free across our remaining prisons.”

Electronic cigarettes have recently been made available in every prison shop at a comparable cost to tobacco.

Peter McParlin, chairman of the Prison Officers’ Association, welcomed the move: “We support a cautious approach to the introduction of a complete ban on smoking. However, we do expect the timetable to be in place and this is made more imperative because of our understanding that the results of air quality tests are worse that could have been expected,” he said.

Peter Dawson, of the Prison Reform Trust, said a sensible and considered approach to smoking in prisons would leave prisoners with a choice – at least to smoke outside. “If that is to be denied to them, there has to be proper support while people give up – not just smoking cessation aids, but increased vigilance for signs of distress that could easily turn into self harm or worse. A hard-pressed prison service will need the breathing space to manage a difficult operational transition.”

