Three members of Lancashire police staff are facing disciplinary action after thousands of motorists were wrongly accused of speeding.
An investigation by the Independent Police Complaints Commission (IPCC) found 2,115 tickets had to be cancelled and 545 convictions overturned.
The IPCC said a speed camera was wrongly set up and paperwork incorrectly processed.
A speed camera operative and two processing unit staff face action.
Two other members of the force's Central Processing Unit (CPU) have been cleared of any wrongdoing.
The speed camera error resulted in 545 unsafe convictions, the refund of £35,000 in fines and the rescinding of 1,500 penalty points.
No criminal charges
The processing investigation meant 2,115 tickets were cancelled and inquiries are under way to find out whether any convictions might have resulted from incorrect paperwork.
The IPCC said that the Crown Prosecution Service had looked at the file, but found insufficient evidence for a criminal prosecution against the speed camera operator.
Naseem Malik, IPCC Commissioner for the North West, said: "The investigations have identified matters that must now be presented before a disciplinary panel and, therefore, it would not be appropriate to go into full details at this stage.
"However it is correct to say that concerns over the work of these individuals has resulted in a number of convictions having to be overturned.
"Once the disciplinary panels have been held, the IPCC will issue further details about the findings of the investigations."
