The Government said last night it was committed to encouraging as many children as possible to walk or cycle to school following the suggestion that car exclusion zones should be set up around schools.

Banning vehicles from the vicinity of schools could help reverse the decline in walking seen in the UK in recent decades, said the Institute for European Environmental Policy (IEEP).

At present, 38 per cent of all journeys under two miles - which could be covered by up to 30 minutes' brisk walking - are taken by car, adding to the "twin crises" of obesity and climate change, the report warned.

If a typical British adult were to walk one hour more a week, it would prevent them gaining two stones over a decade and make a major contribution to halting the obesity crisis.

It could also reduce carbon dioxide (CO2) emissions from cars by 11 million tonnes, or 15.4 per cent, the research said.

Taking children to school is an activity that could be carried out on foot, the institute said. It would benefit both children and parents.

In 1989, adults drove an average of 55 miles for the school run, but that had increased to 82 miles by 2005.

The IEEP report warned that changing behaviour would be a large-scale effort costing millions of pounds. However, a first step could be banning cars from schools or local shops and other facilities where people routinely drive.

The effort would be cheaper than dealing with the cost to the NHS and society of the obesity crisis and climate change, the IEEP's Unfit for Purpose report said.

A Department for Transport spokeswoman said small grants had been awarded to more than 3,000 schools for walking to school initiatives, but the final decision on the restriction of cars would be made by local authorities.

''Some schools already encourage parents to park away from the school gate and walk the last part of the journey with their children," the spokeswoman said.

''Schools often negotiate with local pubs or supermarkets for parents to use their car park to set up a park-and-stride scheme which then forms part of their school travel plan. However, it would be a matter for schools and local authorities to decide whether restrictions for cars around schools would be appropriate for their areas."