400,000 children would be classed as being in poverty if parental tobacco expenditure were subtracted from household income.
Research by the University of Nottingham has found half of the 2.3 million children living in relative poverty in the UK have a parent who smokes.
Dr Tessa Langley, at Nottingham’s UK Centre for Tobacco and Alcohol Studies, who carried out the study said: “This study demonstrates that if our government, and our health services, prioritised treating smoking dependence, it could have a major effect on child poverty as well as health.”
The findings come from the first UK study to highlight the extent to which smoking exacerbates child poverty.
But according to another study, tens of thousands of children have been spared illness and lung infections as a result of the smoking ban in England.
In 2007 a law came into force which made it illegal to smoke indoors and in public places.
This was done to help protect non-smokers from the health risks associated with passive smoking.
The NHS says that passive smoking can damage your body because secondhand smoke contains more than 4,000 chemicals, many of which are irritants and toxins, and some of which are known to cause cancer.
Research by the European Respiratory Journal looked at 1.6 million hospital admissions of under-14s from 2001-12.
It found 11,000 fewer children being admitted to hospital each year with lung infections.
Study author Dr Jasper Been said: “Our results add to the growing body of evidence demonstrating the benefits of smoke-free legislation.”
“Although our results cannot definitively establish a cause and effect, the rigorous analysis clearly shows that the introduction of smoke-free legislation was associated with significant reductions in hospital admissions among children.”
Health experts say that breathing in secondary smoke was previously a major driver of health problems in the young.
According to the NHS website when someone smokes a cigarette, the smoke from the burning tip is released into the air and so is the smoke that they breathe out.
For more information on the dangers of passive smoking or if you are trying to stop smoking visit: www.nhs.uk