The proportion of parents who drive their children to school rather than walk or cycle is on the rise despite growing concerns about the impact of air pollution on young people's health.

New figures from the government's National Travel Survey show that the percentage of primary school children who walk or cycle in England fell from 53% to 51% in 2017.

It also revealed an overall increase the number of people using cars or vans instead of walking for journeys of less than two miles, which campaigners say has a major impact on air pollution and obesity.

Earlier this month, the Guardian highlighted how schools and local authorities across the UK were attempting to crack down on the school run, closing roads, setting up "park and stride" schemes and walk-to-school initiatives, amid mounting evidence of the damage air pollution is doing to young people's health.

Joe Irvin, chief executive of Living Streets, a charity that campaigns to increase walking and cycling, said the figures underlined the challenge of persuading people to abandon their cars for the school run and other short journeys

"The rise in people using their car for journeys that could be walked shows that Britain's illegal levels of air pollution are set to continue."

Irvin called on the government to act decisively to make it as easy as possible for children and parents to walk to school.

Xavier Brice, chief executive of walking and cycling charity Sustrans said the findings highlighted the need for concerted government action on both walking and cycling if it was to improve not only air pollution but childhood obesity.

"These results show the critical need to invest in cycling and walking infrastructure in our towns and cities to enable more people to walk and cycle for everyday journeys. In a week when Public Health England has released its extraordinary findings that one in 25 year six pupils are now classified as seriously obese, we need to do more to enable more children to walk and cycle the school journey."

The Guardian found that thousands of schools in UK cities and towns – from Edinburgh to London, Manchester to Ellesmere Port – are taking measures to try to deter parents using their cars.

Last year, the government set the first target around the school run, aiming to to increase the proportion of primary school children walking to school to 55% by 2025, with funds from the "sugar tax" used to boost PE and sports funding and "active travel initiatives". However, that target is still way below the levels seen a generation ago when, according to Living Streets, about 70% of children walked to primary school.

The findings come amid growing concern about the illegal levels of air pollution in the UK and the impact on human health – particularly that of children. Earlier this month, a medical expert said the hospital admissions of a girl who died from an asthma attack at the age of nine showed a "striking association" with spikes in illegal levels of air pollution around her home in London. Government figures also show a steep rise in the number of deaths from asthma, which experts say could be fuelled by worsening air pollution.

And last year the Guardian revealed that hundreds of thousands of children are being exposed to dangerous levels of air pollution outside schools, colleges and nurseries.

The government has been defeated three times in court over its air pollution plans and is now being taken to Europe's highest court. The UK government's own figures show the school run is a major factor, comprising one in four cars on the road at peak times.

Doctors say children were particularly vulnerable to the impacts of air pollution, with damage to the lungs in early age irreversible, and a clear link between children breathing in dirty air and chronic chest problems later in life.

A Department for Transport spokesperson said the government was committed to making walking more accessible "to everyone through our £1.2bn cycling and walking investment strategy."

They added: "We are taking a number of steps to boost the number of primary school children walking to school, including supporting Living Streets through their 'walk to school' campaign, which aims to make this the natural choice for pupils."