He told the Cape Town Press Club that 87 officers were arrested in the last financial year alone for corrupt activities such as selling drugs to gangsters and participating in armed robberies.
Of these, 20 had been dismissed. The rest were still involved in criminal procedures.
"We also know that some of our police officers hire their guns out to people to commit crimes," Lamoer said.
The department had registered all service firearms on a database to combat this trend.
Lamoer told reporters the province was afflicted by gang-related violence, substance abuse and illegal firearms.
The latest crime statistics released for the province showed a leap in drug-related crime between 2010/2011 and 2011/2012, from 70 588 reported cases to 77 069.
Illegal possession of firearms dropped slightly in the same period from 2 551 cases to 2 395 cases.
Gang-related crime was not indicated in national crime statistics.
Lamoer said the perceptions of communities were a more reliable indicator of crime than national statistics.
"I don't believe in decreases and increases of crime of more than 10% to 15%, to 30%, 40% because something must be seriously wrong in crime [statistics] for it to fluctuate that way," he said.
"We can celebrate the decreases in crime, but what difference does it make to a baby girl of 18 months who was raped? It doesn't make any sense."
He said the job of the police was to ask how they could go back to a community and change the perceptions of where they lived, or of the government that was tasked with protecting them.
Partnerships with various non-governmental organisations played a key role in keeping an ear to the ground and identifying victims, especially women and children.
Lamoer said these crimes were "sad and also very serious", with victims of sexual offences getting younger.
He said on Wednesday morning alone, he had heard of three girls, aged four, five and 10, who were raped in separate cases.
"It is with people that they know: their fathers, their step-fathers."
He said the police had "excellent partnerships" with non-governmental organisations such as Rape Crisis and The Pink Ladies, but more was needed to fight such crimes.
The partnership with the provincial social development department, for instance, was "not up to scratch" when it came to abuse.