Employers are now being urged to educate their company drivers about how the charging system works.
The call comes from Lex Vehicle Leasing, which has paid out more than £600,000 in fixed penalty fines during the first year of the charge.
Managing director Jon Walden said: 'The entire industry has got to act now and improve drivers' understanding of all areas if we are to stop wasting time and money in this area.
'We have all got to take responsibility as the entire situation is getting out of control. Companies are wasting valuable time in administering the penalty tickets, which could be used more efficiently in other areas of the business.'
Almost a fifth of Lex drivers have received a penalty notice and Lex estimates that across a car parc of three million cars, the fleet industry was issued with more than 450,000 notices last year. At an average £40 per fine, it leaves fleets £18 million out of pocket, a problem first revealed in the Fleet News FN50 in October.
Lex has employed a full-time member of staff to deal with congestion charge penalties, which are currently totalling 60 a day.
Debbie Morgan, Lex Vehicle Leasing's general manager of service delivery, said: 'We are seeing a post bag of about 60 congestion charge penalty notices each day, with some drivers being caught three or four times in the same week.
'Some drivers are genuinely unlucky because they have to travel to an address in London that is 100 yards inside the congestion charge zone and haven't realised what they have done. However, most drivers we talk to claim either not to know anything about how the charging works or believe they won't get caught.'