Swedish daily Dagens Nyheter, who took part in the study, report that severe under staffing problems were found in the service.
Isolation was a complaint from inmates who say they lack human contact and get little or no time to communicate with the guards.
The falling staff numbers in the Swedish Criminal Correction System pose a risk for both the employees and the prisoners, says the Committee.
A number of suicides during the last few years has prompted the service to set up a group to try and tackle the problem.
The Swedish Government now has six months to answer the UN report.