Almost 18 million NHS patients in England are registered at GP surgeries located in air pollution hotspots that exceed World Health Organisation (WHO) guidelines, according to a startling new analysis by the UK100 environmental cities network.

Nearly one in three - 30 per cent - of all NHS patients registered in England use surgeries that experience high levels of air pollution, according to the research published today. Together these 17.9 million people are equivalent to the entire population of Greater London and all the 30 largest towns and cities in England combined.

The findings are based on particle pollution (PM2.5) data published by the British Lung Foundation and the NHS Digital Database. It shows that London (7.5 million), the East Midlands (2.1 million), the East of England (2.5 million), South East (2.3 million), and the West Midlands (1.5 million) have the most patients registered with GP surgeries in pollution hotspots.

PM2.5 consists of miniscule particles that are small enough to pass through to the lungs and enter the bloodstream, potentially contributing to a raft of heart and lung problems.

However, the current legal limit for PM2.5 in the UK is twice as high as that recommended by the WHO.

UK100 director Polly Billington said the figures showed air pollution was a "national problem" and called for a new Clean Air Act.

"Some of the most vulnerable groups of people including young children and older people will walk to their GP, often to get help with respiratory conditions like asthma and bronchitis," she said. "This shows the real danger to their health of the air pollution in their communities."

The findings, which are also backed by the chief executive of NHS England, the Mayor of London, and the British Medical Association (BMA), prompted fresh calls for the UK government to unlock new measures and funding to help councils improve air quality in local areas.

The Mayor of London, Sadiq Khan, said the findings were a "timely reminder of how many people are exposed to poor air when they are at their most vulnerable".

"Government must recognise that cities can't win this battle alone and we now need to be given greater powers and funding to clean up our filthy air and protect future generations," he added.

The research comes ahead of a Clean Air Summit in London on Wednesday which will be attended by mayors and council leaders as well as the Environment Secretary Michael Gove and Health Secretary Matt Hancock.

It follows the launch of new government air pollution proposals last month, which include plans for new regulations to tackle emissions from farming, wood-burning stoves, and diesel cars. The government also said it would go beyond existing EU air pollution rules by adopting stricter WHO air pollution guidelines, although critics warned such plans were short on detail with no clear deadlines for meeting these limits.

Also attending Wednesday's summit will be Simon Stevens, chief executive of NHS England, who urged NHS bodies across the country to adopt cross-sector partnerships with local organisations to help tackle air pollution.

"Air pollution causes thousands of hospital admissions and early deaths every year, but while doctors, nurses and therapists are treating the health consequences, the NHS is also taking action to tackle the problem at source," Stevens said. He highlighted the NHS's target to cut emissions from its fleet by 20 per cent by 2024, with at least 90 per cent of vehicles using ultra-low emission engines.

The Department for Environment, Food and Rural Affairs (Defra) was considering a request for comment at the time of going to press.