Hundreds of young drivers could be on the road illegally after being sold invalid motor insurance by an online company, Leicestershire County Council's Trading Standards have said.
Aston Midshires Insurance, based in Enderby, has been selling car insurance aimed at young drivers.
Police, Trading Standards and the Financial Services Authority are investigating the company.
The firm has now removed its website and stopped answering its phones.
'Tip of the iceberg'
Keith Regan, from the county council's trading standards team, said there had been 30 complaints from people who had paid for motor insurance but found it not to be valid.
"I think we've only got the tip of the iceberg," he said.
"We know that the website is linked to foreign addresses.
"The fact that City of London Fraud Squad are involved, it's going to be big," he said.
Leicestershire County Council Trading Standards has urged anyone who has bought their car insurance from Aston Midshires Insurance not to drive until they have legal insurance cover.
"There may be hundreds and possibly thousands of people out there who have got vehicles that aren't insured," Mr Regan said.
"There's consequences not just for them but also for those people they may have an accident with."
Aston Midshires Insurance's headquarters is listed as being at a building on Grove Business Park in Enderby. The company has no offices there and never did, according to the owners of the building.