At the centres, several cases have been reported where police personnel are guilty of physical abuse and excessive use of force against detained individuals, says the European Committee for the Prevention of Torture in a new report.
The criticism comes after visits earlier this year to four facilities where migrants are being held pending deportation.
"The Committee is also critical of the widespread practice of administering non-prescribed psychotropic drugs mixed with water," they write in the report.
The centres' design is also being criticized because they are too similar to prisons, with features such as "triple metal mesh screens and cage-like outdoor facilities".
In defence, Italy argues that the prison elements cannot be removed because it would only lead to "increased escapes from the centres and episodes of vandalism".
Migrants can be held in custody at Italian migration centres for up to 18 months.
