There will be no increase in the fee paid by drivers to enter central London for at least 10 years, Mayor Ken Livingstone has said.
Traffic dropped by 25% last week
Summing up the first full week of congestion charging, Mr Livingstone said the scheme's success meant that "£5 was enough".
He confirmed traffic levels were about 20-25% lower than normal in the charging zone during the first week and 20% lower at the beginning of the second week.
Nearly 7,000 people a day failed to pay the charge, which began on 17 February, with 34,000 penalty notices being sent out.
The mayor said 45 people had incorrectly been sent the fines.
Mr Livingstone said if he wins the next mayoral election in 2004, he would look at extending the scheme to other parts of London.
"We are fine-tuning this system and monitoring it, and by the summer we will be in a position to say if it has been a clear success.
I can't conceive of any circumstances in the foreseeable future where we would want to change the charge
Ken Livingstone, Mayor of London
"Then we could start public consultation about extending the zone so that people going to the ballot box next year will know where everyone stands."
He said he had originally thought the charge would need to be raised to £6.
"It won't now be necessary. It's now quite clear that £5 was enough.
"I can't conceive of any circumstances in the foreseeable future where we would want to change the charge, although perhaps 10 years down the line it may be necessary."
Mr Livingstone said traffic would probably "creep back" into the central zone, but even if levels increased by 5% it would still be in line with the 15% reduction target he had set.
Transport for London director Derek Turner revealed there had been cases, caught on camera, of people trying to change number plates illegally.
He said the information would be passed on to the police.