SPOT checks on taxis in Sheffield found around half failed to comply with rules on vehicle roadworthiness and licensing conditions.
Sheffield Council officers carried out the inspections over a four-month period and of 79 vehicles checked, 41 were found to have defects.
Meanwhile, 18 of 40 drivers’ licences checked were not found to comply with rules and 22 licences were not found to have any faults.
There were also four prosecution cases involving taxi drivers during the period.
Details of the enforcement activity are being discussed at a Sheffield Council licensing board meeting on Tuesday - although the statistics date from the period between November 2011 and February 2012.
Of the vehicles checked, none were found to be in such bad condition they were banned but defect notices were issued in all cases, ordering drivers to make repairs, the council said.
Some 33 black cabs and private hire vehicles were not found to have any defects.
The report to councillors reveals details of the four prosecutions made - which include one driver who was fined £850 for plying for hire without a licence and twice using an uninsured vehicle.
Another driver was fined £60 for refusing to carry a passenger’s assistance dog.
Two other drivers received cautions - one for failing to carry a passenger’s assistance dog and another for failing to declare a previous offence.
There are no pending prosecutions for taxi driver offences, said Steve Lonnia, chief licensing officer at Sheffield Council.
Taxi licensing officers also dealt with complaints from the public about the behaviour of taxi drivers.
The worst spot was Rudyard Road, in Hillsborough.
Mr Lonnia said: “This area continues to be a concern for local residents.
“A number of warning letters and formal warnings have been issued to drivers who have repeatedly transgressed in this area.
“Some 47 warning letters were issued to drivers in 2011 for causing a hazard or obstruction in this road.”