A report by six migrant aid groups says the number of migrant children held in detention and due to be deported rose sharply in 2017. More than half of the children were less than six years old.
The report was published by six French migrant aid associations -- Assfam-Group SOS, Forum Refigie-Cosi, France Terre d'Asile, Cimade, Maltese Order and Solidarite Mayotte.
It says that last year saw 304 children put in immigration detention in France. In 2016, that number was 179.
"The number of accompanied children in certain detention centers has reached a record high, although this type of detention can be easily avoided," the aid groups claim. In France, the law prohibits children from being separated from their parents, so children have to be detained with their families.
The report says that 52 percent of the children detained were less than 6 years old. It also notes that almost 70 percent of the cases related to children due to be deported to another EU country under the EU's Dublin Agreement.
Detention 'deeply traumatizing' for children
"Even a short period in detention with all the characteristics of a prison environment is deeply traumatizing for children," according to the report.
The EU Fundamental Rights Agency has also criticized detention of migrant children and is currently undertaking a study to see how migrant detention harms children. The EU only allows detention of children if there is no alternative and if it is in the child's best interest.
The Cimade organization noted that the temperature in a detention center in the Paris suburb of Mesnil-Camelot was less than 10 degrees centigrade. "We will never forget your inhumane approach, Mr Collomb," Cimade wrote in an address to Interior Minister, Gerard Collomb.
Some opposition members of the French Parliament, as well as some members of Emmanuel Macron's En Marche party, have tried unsuccessfully to ban juvenile detention in France.