Manfred Nowak, UN special rapporteur on torture and other cruel, inhuman or degrading treatment, also denounced "deplorable conditions" including severe overcrowding at pre-trial detention facilities in the former Soviet state.
"Torture and ill-treatment by law enforcement officials still exists in Georgia", Nowak said in a statement issued after a week-long, fact-finding visit at the government's invitation.
In the detention centres where the UN envoy interviewed inmates, he found an "apparent culture of impunity for perpetrators of torture". Despite "a number of substantiated cases, in no instance have the perpetrators been brought to justice", he added.
An Austrian law professor, Nowak met senior officials including Western-leaning President Mikhail Saakashvili - brought to power in a bloodless revolution in November 2003 which toppled veteran leader Eduard Shevardnadze.
He received "clear commitments from the government" and said that authorities at all levels recognised the problems, according to the UN statement issued in Geneva.
Nowak, who also visited prison facilities in the Moscow-backed separatist regions of Abkhazia and South Ossetia, will make a full report to the UN Commission on Human Rights.
The 53-member state forum opens its annual six-week session in Geneva on 14 March.
Georgia sent extra troops to Iraq on Tuesday after requests from the United States and the United Nations, increasing its force there to 850 from 300 soldiers.