The western congestion charge zone will be abolished if Ken Livingstone loses the London mayoral elections in May.
Both Boris Johnson and Brian Paddick have said they would stop charging drivers to enter the area encompassing Kensington and Notting Hill if elected mayor of London.
Critics claim extending the congestion charge has dramatically increased the volume of traffic in the original central zone, with newly eligible residents able to claim a significant discount throughout central London.
Conservative mayoral candidate Mr Johnson agreed the westward extension wasn't working, concluding "I think we should get rid of it".
In an interview with BBC London he said: "We need to have a fairer system, a system which makes use of better technology, and a system which doesn't penalise people who just nip in and out, while some people pay the same for going in eight or nine times a day."
Mr Paddick, who hopes to become the first Liberal Democrat mayor of London, also said he would scrap the westward zone.
Launching his campaign in Brixton, he said he was considering a range of options to reduce congestion, from the "nuclear option" of banning all cars from central London to increasing the daily congestion charge to £20.
Mr Johnson said he would reduce the fine for people failing to pay the congestion charge and give them five days to pay.
The cycling MP also repeated his pledge to cull London's "bendy buses" and cap Tube fares.
Identifying crime as the "number one issue" for Londoners, he said police should use scanners to detect weapons.
Mr Paddick agreed crime is Londoners' "number one concern" and pledged to cut it by 20 per cent during the five-year mayoral term.
The former deputy assistant commissioner at the Met said: "Ken Livingstone has said he cannot do anything about gun and knife crime.
"Boris Johnson has admitted he doesn't have the experience to deal with it. It's time for someone who can stop the slaughter on our streets."
Meanwhile the Conservatives have claimed Labour politicians could receive "golden goodbyes" worth up to £92,000 if they lose their seats in May.
Shadow secretary of state for local government Eric Pickles said: "Local residents will be outraged at cash being stuffed in the pockets of electorally-challenged Labour politicians, and Labour's unpopularity in the polls being rewarded with taxpayers' hard-earned money."
But a spokesman for Labour on the London Assembly accused the Conservatives of hypocrisy as they had supported the relevant proposals when they were discussed in the assembly.
He said: "The reality is that the politicians most likely to benefit from this are the London Assembly Tories, several of whom hold highly vulnerable seats".