Terence Bendixon of the Pedestrians Association on Radio 5 Live

It says that adult levels of fitness and physical exercise tend to be established in childhood and health problems such as obesity, heart disease and hip fracture may worsen unless the decline in walking to school is reversed.

The report, The School Run - Blessing or Blight?, was compiled by researchers at the Institute of Child Health, who analysed published data on changing patterns of school travel over the past 20 years.

The proportion of children aged five to 11 walking or being driven to school

This shows that contrary to popular belief, most primary school children (59%) do still walk to school - but that has fallen from 72% in the mid-1970s.

Ironically, because fewer of those children who do walk to school do so on their own, there has been a rise in the number of adults walking with them - at a time when adult walking as a whole has declined.

Important source of exercise

The main factors leading to the decline in walking to school appear to be "lifestyle" issues, such as rising car ownership, increasing numbers of mothers with cars and parental fears of molestation, abduction and traffic danger - which is exacerbated by the number of vehicles making the school run.

The researchers predict that rising car ownership will probably lead to a further decline in children walking.

They argue that the decline in walking to school is particularly worrying, given the generally low levels of physical activity amongst British children and the importance of the school journey as a source of exercise.

This has implications for both childhood and adult health because sedentary children are more likely to become sedentary - and unhealthy - adults.

Trend

Researcher Dr Ian Roberts says: "Parents drive their children to school to protect them from danger, but they are increasing the risks of obesity and dependency and establishing behaviour that will undermine their children's health in later years.

"Adults are already walking less, with increased risk to their health. The present generation of children, progressively losing the habit of walking to school, will continue the trend.

"And as more parents acquire cars, more children will be driven. While the streets are unsafe for children to walk to school, we are storing up problems for their future health."

Director of the Pedestrians Association, Ben Plowden, said: "Everyone knows that the growth in the school run has been a very mixed blessing. This report shows just how big the costs may be.

"Rising car ownership, time pressures and fears about paedophiles and traffic make the school run seem unavoidable for many parents. But the resulting air pollution and traffic damage the health of children who do still walk to school.

"And now it looks like the school run may be bad for the health of the children being driven, let alone their future health as adults."