Objectives To investigate parental smoking behaviours between England and Scotland after the smoke-free legislation in Scotland came into effect in 2006 and examine inequalities in maternal smoking behaviours between countries.

Methods 5954 white mothers and 3757 fathers resident in England and 1522 white mothers and 904 fathers resident in Scotland who participated in the Millennium Cohort Study (a prospective nationally representative cohort study) when the cohort child was age 9 months (before legislation) and 5 years (after legislation in Scotland but not in England). The main outcome measures were smoking at 9 months and 5 years, quitting smoking by 5 years, starting smoking by 5 years.

Results In England and Scotland approximately 30% of parents reported smoking at 9 months with only a slight decrease in smoking at 5 years. There were no differences between countries in parental smoking after the smoke-free legislation in Scotland came into effect, taking into account prior smoking levels. Light smokers (1–9 cigarettes/day) from Scotland were less likely to quit by 5 years than those from England, but there were no differences between countries among heavy smokers (10+ cigarettes/day). Non-smoking mothers from Scotland (6.2%) were less likely to start smoking by 5 years than mothers from England (7.3%). Mothers from more disadvantaged circumstances in both countries were more likely to report that they smoked or started smoking. In England quitting was also socially patterned, but in Scotland, after the legislation was introduced, the gradients in quitting smoking were flatter across social groups.

Conclusions Smoking behaviours among parents with young children remained relatively stable, highlighting the need for additional tobacco control efforts to support smoking cessation. However, the smoke-free legislation does not appear to widen health inequalities and may even help reduce them by encouraging quitting across socioeconomic groups.