Fleet managers have been warned that company car drivers who do not report serious health conditions could be driving illegally.
If drivers fail to disclose important information to the DVLA, particularly about medical conditions, their driving licences could be invalid.
There are a number of circumstances where the DVLA can revoke a driving licence.
"All drivers are required by law to notify the DVLA of any medical condition which may affect their fitness to drive, but many drivers are failing to report this and could be using the roads illegally,” said Gavin Jones, risk management expert at Masterlease, said.
”When the DVLA is notified of any medical issues, a full investigation is carried out before the motorist is deemed fit to continue with their licence.”
Other circumstances include lack of awareness of the new Drivers Act, which states that a new driver must serve a probationary period of two years when they become qualified.
Motorists who accumulate six or more penalty points during the first two years of driving will automatically have their licences revoked by the DVLA.
“Many young, newly qualified drivers do not realise that they have to serve a probationary period and therefore fail to surrender their licences if they receive more than six points in that time frame,” said Mr Jones.
“More fleet managers need to be aware of the current laws in place when it comes to surrendering licences and have written policies stating that if drivers do not follow the procedures they are breaking the law and putting other motorists at risk.
"In the event of an accident the driver's insurance would be void costing both parties financially, let alone any potential hazards to other road users."