Drivers who miss three payments will have their cars clamped and face a bill of more than �500 to get them back.

Motorists wishing to drive into central London will have to pay the �5 toll from February 2003.

But Mayor of London Ken Livingstone said persistent evaders will not be allowed to get away without paying the charge.

Hardened criminals

He told BBC London: "What we are not going to have is only the person who just occasionally makes mistakes and gets fined paying, while hardened criminals who day after day abuse the system get away with it."

But the AA has raised concerns that innocent motorists may find their cars ending up in the pound.

Spokeswoman Rebecca Rees said: "We are worried that, because the DVLA records are so out of date with about 12m vehicles unaccounted for, the wrong people could end up having their vehicles clamped and towed away.

"We would want absolute guarantees that a very thorough cross-checking system was in place so only those who are dodging the system ended up being punished in this way."