The committee called the centre at Ellebæk in North Zealand “unacceptable for people”.
The Strasbourg-based European Committee for the Prevention of Torture (CPT) is the anti-torture committee of the Council of Europe.
The report is based on visits to Ellebæk and other detention centres including Nykøbing Falster Arrest.
Both facilities house migrants who are under arrest based on Denmark’s immigration laws (Udlændingeloven), but not for committing crimes.
In the report on Denmark, which was published on Tuesday, the CPT calls Ellebæk one of the worst facilities of its kind in Europe.
“In our view it is unacceptable to keep people in (prison)-like conditions and furthermore with (poor) sanitary conditions and bad hygiene,” Hans Wolff, the leader of a delegation which visited Ellebæk in April last year, told TV2.
“There are a lot of reasons why Denmark is proud of its human rights (record), but when you come to these places and you find such appalling conditions then one might question either the capability of Denmark to do it better or maybe the will of Denmark to do it in such a bad way,” he added.
“It is not compatible with human rights to keep people under such bad conditions in immigration detention centres,” Wolff also said.
Migrants at the two centres are not suspected or convicted of any crime, the report stresses.
One specific criticism in the report is of only 30 minutes’ daily access to outside exercise provided at Ellebæk.
Another involved punishment for use of mobile telephones.
Meanwhile, the use of restrainment was also criticized as potential abuse.
“The Committee expresses its serious misgivings that the application of the prison rules led to a situation where detained migrants who were found in possession of a mobile phone had to be punished by law with at least 15 days of solitary confinement,” the report states.