Harlesden and Neasden are home to three of Britain’s 10 worst polluted areas, a new index of toxic air shows.

Friends of the Earth analysed councils’ most recent annual Air Quality Status Reports, submitted to the government to show much nitrogen dioxide is in the air we breathe.

Three areas in Brent saw average annual levels at nearly three times the European target of 40 micrograms per cubic metre.

North Circular sites Chartley Avenue, in second place, and Ikea in Drury Way, in third place, averaged 115.39 micrograms and 102.1 micrograms respectively. Harlesden High Street in ninth place had levels of 91.83 micrograms per cubic metre.

Fiona Mulaisho, chair of Clean Air for Brent, said: “It’s extremely worrying that, of the top 10 worst areas for breaches in the country, three are in Brent. The figures are alarming, critically in excess of the European limit of 40 that’s deemed fit for humans.

“These areas where these breaches are reported are heavily populated by humans.

“Harlesden High Street is a bigger worry as it’s near to John Keeble school – which, along with Ark Franklin Academy in Chamberlayne Road, are the two worst polluted schools out of 50 in the mayor of London’s air quality report.

“Think of the millions of people who go to Ikea.”

She added: “We’re very disappointed that air quality is not prioritised in the way that it should be given the disastrous and devastating impact that it has not just on humans but inevitably on Brent’s economy due to illness.”

Dr Penny Woods, chief exec of the British Lung Foundation, called the analysis “shocking, but sadly not surprising,” adding: “High levels of NO2 can irritate and inflame the lining of the airways, causing a flare-up of asthma or COPD and symptoms such as coughing and difficulty breathing.

Simon Bowers of Friends of the Earth said: “The government needs to step up and do more to help deal with this air pollution crisis – they can’t just carry on leaving the difficult decisions with local authorities, many of which are severely under-resourced.”

The council said it is working on several initiatives to reduce carbon emissions.

Highways chief Cllr Shama Tatler said: “Helping people to change bad habits and make better choices will play a big part in tackling poor air quality in our borough.”