More than a third of taxis checked during a police operation were flouting rules, as officers also made an immigration arrest.
Herts Police worked alongside enforcement representatives from TfL and Wolverhampton Council to stop and check 32 drivers in Three Rivers on February 25.
Of these, 12 were found to be non-compliant with their conditions and further enquiries with the relevant authorities were triggered.
Problems included low tyre tread and not correctly displaying badges, with drivers told to rectify any issues during the operation.
Community Safety Unit Sergeant Gary Yam said: “This is just one example of how we work alongside local partners to help keep people safe.
“While the majority of the vehicles stopped were compliant with their licence conditions, there were a few issues which needed to be addressed.
"I’d like to thank everyone involved for their efforts.”
The drivers came from five local authorities. TfL and Wolverhampton officers were part of the operation because many vehicles in Three Rivers are licensed in those areas.
City of Wolverhampton Council has been described as having a quicker and cheaper taxi licensing application process than other areas, leading to taxis licensed there operating across the country.
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The council has stressed that it is illegal to refuse applicants a taxi licence because of where the applicant lives, with proponents describing its process as more efficient but just as rigorous.
Herts Police added that they spotted a man illegally riding an e-scooter on a pavement during the operation. Enquiries led to the rider being arrested over immigration offences and the e-scooter was seized.
Further information has been sought on the immigration arrest. Update to follow.
