A squad focusing on organised crime has been shut down so police can focus on attending burglaries, according to a frontline officer.
The officer said frontline police were spread too thin and could not do more without more staff.
"We're robbing Peter to pay Paul and the sums don't add up. If we want to make a dent in these burglary stats, perhaps shutting down a squad focusing on organised crime isn't the way to go," it said.
"If I believed we had the capacity to attend every burglary, I'd be 100 percent behind this idea, but we're only chasing our tails. The only solution is more staff. With successive frozen budgets, we're at rock bottom."
Police Association President Chris Cahill said officers were finding it tough.
"When we last surveyed all our members, one of the key things that came out was they didn't believe they had the resources and capability to give the public the service their communities deserved, and what they wanted to do.
"So that can be quite unmotivating at times."
Cutting the number of police dealing with organised crime was what often happened when more officers were needed elsewhere, Mr Cahill said.
"In some ways organised crime is the easiest one to move staff away from because if you don't generate the work, you don't see what's happening.
"But we would argue that organised crime and drugs are one of the key drivers behind a lot of crime, such as burglaries," he said.
Green Party police spokesperson David Clendon said Ms Collins' strategy was not working.
"As one form of offending gets prioritised because of legitimate public concern or expectation, instead of adding more resource to the police, the minister simply is shuffling the cards really," he said.
"So in time we'll see this inevitable roundabout."
Ms Collins said she would not comment on the letter because she had not seen it "and because actually it is the police union newsletter and actually if they want to talk to me that's fine."
Labour police spokesperson Stuart Nash said the government needed to boost police numbers, and start telling the public when it planned to do that.
"The minister said yet again in the House that she has been telling me to wait and she will give me more numbers and I'll be surprised.
"She's been saying that for six months.
"How long do Kiwis have to wait before there are more police out there?
"When you're getting men and women, who are absolutely committed to the police force, saying 'we have concerns', I think the minister should listen."
The Labour Party has pledged to increase police numbers by 1000 during its first term, if elected to government.