Thousands of children are facing hospital this winter as cold weather and the UK’s air pollution crisis combine to create potentially deadly conditions for young people, doctors have warned.

The Royal College of Paediatricians, the Royal College of Physicians and children’s charity Unicef say that the UK’s toxic air and cold weather will leave a huge number of children extremely vulnerable this winter, creating an “overlooked” emergency for an already stretched NHS.

“Wards could soon be filled with wheezing, spluttering children, their lungs struggling to battle the double burden of cold weather and toxic air,” the groups state in a letter to the Guardian.

Winter often sees spikes in acute air pollution as the cold weather results in both an increase in emissions from the heating of homes and offices, including the burning of wood or coal, and reduced dispersion in cold, still conditions.

This, combined with freezing temperatures which weaken those with existing respiratory trouble, leaves thousands vulnerable to acute health problems.

In the letter the doctors state that children are most at risk from this double threat. And they say that as the NHS prepares for a winter bed shortage, they have a “mandate to flag an issue that is continually overlooked”.

“We know that the elderly are susceptible to ill health caused by the drop in temperatures, but the impact on young children with respiratory conditions, such as asthma, is often disregarded,” they say.

They say the UK is home to more children suffering from respiratory conditions than anywhere else in Europe. “Admissions for people with respiratory conditions almost double during the winter – and the majority of those admitted are young children,” they say.

“Emergency admissions and mortality rates linked to these conditions are also the highest: a child experiencing an asthma attack is admitted to hospital every 20 minutes.”

Air pollution kills tens of thousands of people each year across Britain and affects the health of hundreds of thousands more.

Last month, the UN warned that the UK government was endangering people’s health by denying their right to clean air, and Unicef told the Guardian it had refocused its British operation to tackle air pollution because of the scale of the “health crisis” facing young people in the country.

In October, the World Health Organization (WHO) said air pollution was the “new tobacco”, causing 7 million deaths around the world and harming billions more. And a recent study published in the Lancet medical journal found that pollution from diesel vehicles was stunting the growth of children’s lungs, leaving them damaged for life.

Health experts say that, on top of respiratory conditions such as asthma, emphysema and bronchiectasis, toxic air causes a range of deadly conditions from heart problems and cancer to strokes, dementia and reduced cognitive ability.

In 2017 the Guardian revealed that hundreds of thousands of children were being exposed to illegal levels of air pollution from diesel vehicles at schools and nurseries across England and Wales, with the poorest neighbourhoods most severely affected.

The government has been widely criticised for its failure to tackle the issue successfully and has lost three court cases challenging its policies.

However, ministers say there is a £3.5bn plan to reduce harmful emissions, adding that their new clean air strategy has been welcomed by the WHO.

They also point out that the forthcoming environment bill will also include provisions to improve air quality, although no details are available.

In the letter, doctors’ leaders and Unicef say more needs to be done to prevent thousands of young people falling seriously ill this winter with “irreversible damage to their health and their futures”.

“The undeniable truth,” they say, “is that most of these cases are preventable. This is an appalling breach of children’s right to survive and thrive.”