Traffic jams of the data variety are locking up the website for Londoners affected by the imminent congestion charge.

Lots of people are visiting the site to register before the charge is introduced on 17 February.

But the large numbers registering for the charge or trying to pay before they travel next week are reporting that the site is being unresponsive.

A study of the site by usability experts show that it ignores basic rules of web design and makes the process of registering unnecessarily difficult.

Charge code

The study of the site was carried out by The Usability Company which advises firms on how to make websites easy to use.

Experts from the company put the site through its paces on 12 February and found that it was struggling to cope with the numbers of people using it.

Most frustrating was attempting to register for the charge. At times the site took minutes to respond as the testers went through the seven stage Fast Track registration process.

Similar frustration was felt by the testers when they failed to get a response from the server taking payments for the first day of the charge's operation.

The Usability Company warned that any bad experience charge payers have with the website are likely to fuel resentment against the charge.

The company also said the website ignored customised browser preferences, has no helper, or alt tags and is difficult for the visually impaired to use.

Tory MP Michael Fabricant added to the criticism of the congestion charge website saying that the mobile phone registration system did not seem to be working.

Responding to Mr Fabricant's criticism a spokesman for Transport for London, which is administering the charge, said earlier problems with the website server had now been put right.