High levels of air pollution are to hit central London today.
The warm weather is pulling hot air in from France, bringing dense smog with it.
Older people and those with asthma or lung problems are being urged to take extra care.
A new Parliamentary report into air pollution recommends that more needs to be done to protect people from harm.
Commenting on the report London Assembly Labour Group Environment Spokesperson Murad Qureshi AM said:
"This report is a devastating indictment of a Mayor and Government who have failed to tackle one of London's biggest environmental and public health challenges.
"Having ignored this problem and blustered his way through for six years, this report finally debunks the Mayor's claims to have cut air pollution.
The report recommends a ban on building schools, hospitals and care homes next to air pollution hotspots caused by road traffic.
The government made the decision after air pollution levels exceeded safe levels for 5 days in a row in the French capital. French experts say the move - last used in 1997 - does have an impact on improving air quality.
Public transport was made free of charge on Friday and today in an attempt to encourage Parisians to leave their cars at home.
The 50 most polluted roads in the UK are all in London. Even number 50 on the list is two and a half times the legal EU level.Read the full story ›
Since the Mayor was elected, NO2 emissions have reduced by 20 per cent and the number of people living in areas exceeding NO2 limits has halved but he fully recognises the need to take further action.
This includes the introduction of the world's first Ultra-Low Emission Zone in central London from 2020, tougher requirements for taxis from 2018 and a £20million fund to tackle local problem areas.
These most ambitious measures will deliver enormous economic and environmental benefits for central London and will make this global city an even better place to live, work and visit.
The toxic gas nitrogen dioxide (NO2) can lead to respiratory disease and can cause the lining of the lungs to become inflamed.
The government is the subject of legal action after failing to deal with the high level of the toxic gas in the country's cities.
Most British cities have plans to reduce traffic fumes to within the legal limit by 2020, however London has insisted that it could not meet the NO2 targets set for it in 1999 until at least 2025.
London has the highest levels of NO2 of any European capital city and the UK has the highest proportion of zones breaching legal limits.
Other highly polluted areas include Oxford Street near Marble Arch, which registered at 150 micrograms, and Cockspur Street near Trafalgar Square on 138 micrograms.
The fourth and fifth locations were Park Lane and Knightsbridge - which measured 135 and 134 micrograms respectively.
Grosvenor Place, which runs alongside the Queen's London residence, had the highest level of the toxic gas nitrogen dioxide in 2012.
Researchers found 152 milligrams of the gas per cubic metre of air, with a main contributor being diesel engine fumes. The EU legal limit is 40.
The European Commission has launched legal action against the UK for failing to control air pollution in 16 areas across the UK.Read the full story ›
All of Camden’s main roads break the European legal limits for nitrogen dioxide, along with the City of London and Kensington and Chelsea.Read the full story ›