Capita, the company administering London's controversial congestion charge scheme, has described the glitches suffered by the system following its launch earlier this week as "teething problems".
A spokesman for the services giant said, "It is inevitable that we will have some teething problems in a scheme of this size. However, we are confident that it is working smoothly."
The spokesman said that a fall in national telephone network capacity had resulted in a slowdown on the congestion charge website earlier in the week, although he said that this lasted no more than 20 minutes.
Problems with a credit card number recognition system, which affected a handful of users, had also been quickly resolved, he added.
"Less than 10 people were affected and the problem was rectified within a few minutes," he said.
Last year, Transport for London awarded Capita a five-year contract worth around £230m to administer the congestion-charging scheme, with a possible two-year extension.
Yesterday Capita unveiled its preliminary annual results, reporting a 30% increase in turnover to £898m. In his statement, the company's chairman Rod Aldridge predicted that Capita would be well placed to help other cities follow London's lead.
He said, "More than 35 major cities in the UK have expressed interest in the congestion charging scheme and will be watching the London solution as a way of reducing congestion."
"The fact that Capita has built a scalable, modular solution will give us a very significant 'first mover' advantage," he added.
A spokeswoman for Transport for London said the organisation was pleased with the congestion charging system's first full week of operation.
"We are very pleased with how it has gone so far - we have had very few complaints and very few problems. We are doing everything within our powers to keep errors to an absolute minimum."
TfL said that by 10am yesterday more than 300,000 people had paid the congestion charge.