Diesel cars that do not meet the Euro 6 emissions standard will have to pay a £10 charge to enter London in an effort to combat air pollution.
The Mayor of London, Boris Johnson, will also lobby the Government to raise road tax on diesel cars to encourage motorists to switch to cleaner vehicles, according to The Times.
Fleet News first revealed the Mayor's plans for an Ultra-Low Emission Zone (ULEZ) in April.
The zone will circle an area of central London that is expected to be based on the existing congestion charging zone. The ULEZ will operate 24 hours a day, seven days a week, and will take effect in 2020.
However, the new Euro 6 rules will become standard on all new registrations from September, 2015, so it is not expected to penalise the vast majority of fleets which operate cars on a three, four or five-year cycle.