The LEZ was introduced by Johnson’s predecessor, Ken Livingstone, to improve the air quality in the capital by encouraging the replacement of gas-guzzling vans and lorries with new, greener models.
The scheme, as it currently stands, consists of a £200 charge to all polluting vehicles over 3.5 tonnes failing to meet the required emissions standards, with a possible £1,000 fine.
Phase three, due to launch in October next year, would have targeted some 90,000 smaller vehicles, imposing a daily £100 charge on those that did not meet the emissions standards.
Johnson believes that this additional tax would place an unnecessary burden on small businesses, especially the "white van men" that conduct business in the capital.
"I want to do all I can to ease the burden of the economic downturn that is affecting us all at this time," he says. "Although the low emission zone has been successful in tackling the worst polluters, and will continue to play an important role, it is not the right time to press ahead with extending it to include smaller vehicles like vans and minibuses. Many of these will be owned by small businesses, charities and self-employed Londoners already hard hit by the recession.
"I am confident that we can lower emissions in more imaginative ways," Johnson concludes.