London mayor Boris Johnson has dismissed research conducted by King's College London which found that Oxford Street has the world's highest levels of pollutant nitrogen dioxide, saying the idea it is the most polluted street in the world is a "ludicrous urban myth".

NO2 is produced by diesel fumes coming from buses and taxis and is linked with asthma and heart attacks, with a monitor having detected peak levels of 463 micrograms per cubic metre in the shopping district.

When challenged about it on Twitter, he insisted that London's air quality is "better than Paris and many other Euro cities" and drew attention to the low emission buses and taxis being implemented in the capital.

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He also suggested the user sample the air in Beijing before making such a remark, a comparison Paul Regnart, who researches hydrogen vehicles, wasn't impressed by.

Here's the exchange:

Traders have been calling on Mayor Boris Johnson to reduce the "wall of buses" that stack down the street.

"We are working closely with the relevant London authorities to look at longer term traffic reduction initiatives and we are keen to see ideas rapidly put in place," said Richard Dickinson, chief executive of New West End Company, which represents traders in Oxford Street. "Businesses in the West End want action."

Regnart told the Guardian of his Twitter argument with the mayor: "His response showed it’s obviously an issue because he wouldn’t respond so many times [otherwise]. But the contemptuous response shows it hit a nerve. I wanted to get a reaction, which is what I got."