The scrapping of the western extension of the congestion charge zone is a "democratically right thing to do", London Mayor Boris Johnson has said.
People voted in favour of getting rid of the zone in a consultation after Mr Johnson made the promise to listen to them during his mayoral campaign.
The western zone will be scrapped on 24 December. Transport for London (TfL) estimates it will lose £55m a year.
A green campaign group has warned of a "dangerous" rise in air pollution.
Drivers are charged £8-a-day when they enter central London and the western extension zone (WEZ), but from Christmas Day the WEZ will cease to exist and from 4 January the congestion charge will go up by £2.
Small cars which have low emissions will be exempt from paying the daily toll. TfL has asked motorists who regularly drive into central London to register with an auto top-up system to avoid being fined.
'Dangerous air pollution'
The WEZ was introduced in 2007 by the former Labour mayor Ken Livingstone, despite people covered by the area voting against the proposal.
Defending his decision to get rid of the WEZ, Mr Johnson said: "The effect on both pollution and congestion, we think, will be vanishingly small and it is worth doing just because it was a democratically right thing to do.
"Don't forget I campaigned to consult people properly. The issue was that this thing was put in without a proper democratic consultation."
Simon Birkett, from Campaign for Clean Air, who has threatened to sue the mayor for scrapping the WEZ, said: "We are very concerned the mayor's mitigation measures won't be adequate and the level of dangerous air pollution will rise in this area and that's why we are considering legal action."
Val Shawcross, Labour London Assembly member, said: "We are all going to end up paying for this in massively increased public transport fares."