An investigation into the limousine industry has revealed links to organised crime.
The operation - the first of its kind in the UK - also found many of the luxury cars are unsafe and pose a risk to passengers, the Association of Chief Police Officers (Acpo) said.
Stretch limousines were targeted over the past month in a crackdown on the largely-unregulated industry.
Police seized three vehicles and arrested five people. Another 12 limousines were taken off the road.
Officers uncovered links to "organised criminality" and found a number of "cloned" vehicles. The operation has led to "several large-scale investigations", Acpo said.
There are currently more than 6,000 limousines in the UK. Most have been imported from the US and do not meet UK safety regulations.
Chief Superintendent Geraint Anwyl, chairman of the National Roads Policing Intelligence Forum, said: "Stretch limousines are largely unregulated because they fall short of existing legislation.
"However, we know that many of the vehicles are at least five years old when imported and do not meet the technical and road safety requirements for vehicles in this country. They therefore pose a real risk to road safety and to those passengers who travel in them. In addition to this, unlike bus drivers, limousine drivers are not subject to criminal record checks."
He continued: "Early results from the operation show at least 160 stretch limousines were checked in 15 police forces showing an offending rate of 66%. Twelve vehicles were immediately prohibited for serious defects and taken off the road, whilst a further 27 were issued with delayed prohibitions.
"Five people have been arrested and three vehicles were seized. Several large-scale investigations are currently under way in different parts of the UK as a result of this operation."
