Figures released by the Assembly of French Departments (ADF) have revealed that underage migrants cost French taxpayers two billion euros per year.
Around 41,000 migrants under the age of 18 currently reside in France, 95 per cent of them being male, and cost the French state around 50,000 euros a year each, a report from Agence France-Presse states.
Most of the underage migrants are from Sub-Saharan Africa according to the ADF which says they represent around 15 to 20 per cent of all minors who receive social assistance in France.
The ADF notes that since the height of the migrant crisis in 2015, the number of minor migrants in care of the state has dramatically increased, with the figure going up by 74 per cent from 2016 to 2017 alone.
When a migrant claiming to be a minor arrives in a French department, the government has five days to speak with the migrant and find out details of their background.
Since January, departments are also able to request biometric data such as fingerprints to determine the origin and, through a court order, are able to perform tests to determine the age of the migrants.
According to the ADF, around half of the migrants tested on their age turn out to be adults.
Earlier this year in Angoulême in south-west France, a migrant attempted to claim that he was 17 years old but when authorities connected his fingerprints to a passport he had previously used, they found he was actually 47.
Last year in April, police in Montpellier busted a network of migrants who were using forged documents to claim they were underage. Authorities traced the fake documents to a civil servant in the Ivory Coast who was then arrested.
Last year, France saw a record number of new asylum claims with 123,625 migrants attempting to claim asylum, up 22.7 per cent from 2017 which had also been a record-breaking year.