Pollution in the air is leading to an invisible public health crisis that kills tens of thousands of Britons each year and shortens the lives of nearly 200,000 others, according to experts.

With this week marking 55 years since the 1956 Clean Air Act, campaigners say action on a similar scale is needed once more. A coalition including Asthma UK, Campaign for Better Transport and Friends of the Earth will launch a "healthy air" campaign on Tuesday calling on the Government to act. The new threat is far less obvious than the visible levels of smog of the early 20th century. They are not seen to the naked eye, but tiny particles of pollutants known as particulate matter can be deadly.

About 30,000 people died from air pollution in Britain in 2008, said Professor Frank Kelly of the Environmental Research Group at King's College London. At a recent inquiry into air quality by Parliament's Environmental Audit Committee (EAC), he warned: "We have this new problem that we cannot see: it is tiny particles of nitrogen dioxide." The lives of 187,000 people who die from heart disease have been shortened as a result. "If we consider the air pollution component ... then probably those individuals are losing on average three years of their life."

Joan Walley MP, EAC chair, said: "It's a scandal that the same number of people are dying of air pollution in London now as back in the 1950s. The Government needs to step in."