One in three pregnant women in Blackpool smokes, latest research has shown.
The survey found 33% of women in the Lancashire resort smoked while they were pregnant in 2008-09, compared with just 4% in Richmond, Surrey.
The Association of Public Health Observatories (APHO) figures showed nearly 15% of women who gave birth across England that year smoked.
Overall, deaths from smoking-related diseases across England have fallen.
The charity's survey, commissioned by the Department of Health, found tobacco still caused more significant illness and deaths across the North West than in most other parts of the country.
But the North West also has some of the highest quit rates in the country and downward trends for the main smoking-related illnesses including heart disease, cancer and strokes.
APHO found that, despite the area having the highest number of pregnant smokers in the country, those levels were falling due to continued investment in support for families.
The survey found there were 207 smoking-related deaths per 100,000 people aged 35 and over in England during 2006-08.
This was down from 216 deaths per 100,000 in 2004-06.
Smoking-related deaths from lung cancer were highest in Middlesbrough, with the illness claiming 71 victims per 100,000 in 2006-08.
This compared with 19 per 100,000 smokers dying from lung cancer in Guildford in the same period.
London Health Observatory director Dr Bobbie Jacobson said: "The significant proportion of women who reported smoking in pregnancy is a sign of our need to redouble our preventative efforts in primary and maternity care."
Speaking about all the findings, she said: "There is clearly a mix of good and bad news.
"The overall picture of falling death rates is encouraging and shows what can be achieved over time through clear plans to tackle the harm from smoking."
But she added: "The north/south inequalities remain a stark reminder that the biggest burden of smoking-related ill health still falls on our poorest communities."