Mothers who work raise unhealthier children than those who stay at home, researchers said today.

Children whose mothers are employed are more likely to be driven to school, watch TV, snack on fizzy drinks and eat too few portions of fruits and vegetables, a study found.

The research, on more than 12,000 British schoolchildren, was published in the Journal of Epidemiology and Community Health.

Mothers who worked full-time had the unhealthiest children, followed by those who worked part-time.

A total of 30 per cent (4,030) of the mothers had not worked since the birth of their child but the rest (8,546) were employed.

They typically worked 21 hours per week (with a range of 16 to 30 hours) and for 45 months (with a range of 25 to 55 months).

The mothers were questions about the hours they worked and their children's diet, exercise and activity levels when the youngsters were five.

This included how much sweets and crisps, sugary drinks, fruits and vegetables the child ate and drank, and whether they took part in organised exercise and how they got to school.

Mothers were also asked how long their child spent in front of a TV or computer each day.

Overall, many children had habits that could lead to them becoming overweight.

For example, 37 per cent of children mostly ate crisps or sweets between meals and 41 per cent mostly drank sweetened drinks.

A total of 61 per cent watched television or used the computer for at least two hours a day.

But when the researchers took away factors that might influence the results, such as socio-economic background, they found a definite link between a mother working and the child's' health.

The researchers, from the Institute of Child Health in London, said: "Children whose mothers worked part-time or full-time were more likely to primarily drink sweetened beverages between meals (compared to other beverages), use the television/computer at least 2 hours daily (compared to 0-2) or be driven to school (compared to walk/cycle) than children whose mothers had never been employed.

"Children whose mothers worked full-time were less likely to primarily eat fruit/vegetables between meals (compared to other snacks) or eat three or more portions of fruit daily (compared to two or fewer)."

The researchers also looked at whether flexible working had an impact, but found no strong effect on the health of the children.

The researchers called for more support for working families and concluded: "Currently, approximately 60 per cent of women with a child aged five or younger in the UK or USA are employed.

"For many families the only parent or both parents are working.

"This may limit parents' capacity to provide their children with healthy foods and opportunities for physical activity.

"Policies and programmes are needed to help support parents and create a health-promoting environment."