As many as two-thirds of pubs in the most deprived parts of England could be exempt from a ban on smoking because they do not serve food, according to a study by doctors.

The measures in the white paper on public health, which are supposed to reduce the health gap between rich and poor, could have the opposite effect, say the authors of the study published this week in the British Medical Journal.

Most pubs in affluent areas serve food and so will be banning smoking. But research by the British Medical Association this year revealed that nine in 10 of the local authorities with the highest proportion of non-food pubs were in the north of England and the Midlands.

Leeds topped the league, with 88% of its pubs not serving food and therefore likely to be exempt from the smoking ban, followed by Stoke, Lambeth, Chesterfield, Sunderland, Bradford and Macclesfield.

The new study involved finding details on 174 pubs in the borough of Telford and Wrekin. The pubs were mapped by postcode to establish the deprivation status of each area.

The researchers found that 99 pubs (57%) served catered food; the other 75 (43%) would be exempt from the ban. If licensed private clubs were included in the list - places that can choose but are assumed to want exemption - the proportion without a smoking ban would rise to 56%.

Telford and the Wrekin is similar in social composition to the remainder of the country, the paper says. The authors estimate, based on the above figures, that two-thirds of English pubs in deprived areas would be exempt, compared with only a quarter in affluent areas.

When members' clubs were included, two-fifths of establishments in affluent areas and four-fifths in deprived areas would escape the smoking ban.

"Our results suggest that people in deprived areas are more likely to live near pubs exempt from legislation to protect them against smoking. This is likely to worsen inequalities in health and smoking prevalence," say the authors. "The UK government's white paper, Choosing Health, estimates 'only 10-30% of pubs could be smoking', but our data suggest the proportion of exempt pubs is higher."

Peter Maguire, deputy chairman of the BMA's board of science, said the study showed that a partial ban would "penalise the poor and worsen health inequalities". He added that the only way forward was for England to follow the example of Ireland, and the plans proposed for Scotland, by introducing a total smoking ban in enclosed public places.