A BBC investigation has found that hundreds of London minicab drivers may be working fraudulently after buying qualifications.
A BBC undercover investigation has exposed colleges cheating the on the mandatory exams to get a licence in London.
Under the cab application process, along with a criminal record check and medical test, drivers must sit a topographical exam and an English test at one of eight official TfL testing centres.
Evidence of these exams can also be accepted via other qualifications including BTecs, which are usually taken at private colleges and centres.
The qualification can be used to gain a minicab licence from many councils across the UK.
According to the report, one of these colleges, Vista Training Solutions in Newham, east London, offered to take the tests for several BBC researchers for £500 per BTec.
At a mandatory English and maths assessment answers were read out to eight candidates taking the BTec fraudulently.
Registers were falsified before the online BTec exam was taken by the managers on the candidates' behalf.
The researcher, who had neither attended any classes nor completed an exam, received a BTec level two certificate in Introduction to the Role of the Professional Taxi and Private Hire Driver.
Another undercover BBC researcher, who had also done nothing other than pay, subsequently received a certificate stating he had passed his BTec level two.
Transport for London (TfL) said it would immediately investigate at least 1,667 applications in light of the evidence.
TfL, the licensing authority, said it was "deeply concerned" by the findings.
Caroline Pidgeon, deputy chair of London's Transport Committee, said: "Passengers are getting into those vehicles, and they need to know they're safe.
"To hear parts of that (qualifications) are being forged around London, that's not right, that's really worrying and TfL need to get a grip on this."
Helen Chapman, a director at TfL, said: "It is deeply concerning to learn that some colleges or schools could be illegally providing certificates.
"We will support the relevant authorities with any wider investigations into these organisations. We will take immediate action against any driver identified as fraudulently obtaining a licence."