Up to a quarter of Gardai surveyed are taking DNA samples without being properly trained.
The Garda Professional Standards Unit report for 2018 says there is a lack of oversight and governance in sending DNA for forensic analysis.
Staffing levels at the National Forensic Coordination Office are an organisational concern as many Gardai have not received adequate training in how to handle DNA materials.
Some Gardai said they used a ‘how to’ videos on their internal web page to help them carry out DNA sampling duties.
It found only 55 percent of Garda members interviewed had received training for taking, submission, retention and destruction of DNA samples, while 81 percent of those interviewees are actually engaged in taking DNA.
The internal Garda watchdog says the issue requires urgent attention.