Operation Seahog, a police and Security Industry Authority clampdown on rogue security firms in Liverpool, has prosecuted 184 people in the past two years.
The police campaign was launched in summer 2006 after an escalation in problems with rogue companies taking business away from legitimate firms, especially those protecting construction sites across the city.
Since the scheme was launched, Merseyside Police officers have visited more than 970 construction sites, executed 64 warrants and investigated 52 private security companies. Some 184 individuals were dealt with in court for working without an SIA licence, and a further eight security firms were dealt with for employing security guards without an SIA licence.
Superintendent Paul Richardson said: "Operation Seahog was set up with the express intention of cracking down on those criminal gangs who were running the city's security at the expense of legitimate firms.
"Two years later we can see that is has been an unqualified success and we are now in the position where many more properly licensed and approved contractors are the ones providing security services.
"There is still a long way to go, however, and Operation Seahog will ensure that we get there."