By Peter Allen
The child identified only as Daniel is the son of an illegal immigrant from the Paris suburb of Juvisy.
Last Thursday the pair were arrested as they returned to their car after visiting a leisure centre.
Police officer claimed they were carrying out routine vehicle checks before arrested both father and son.
They were taken to Juvisy Police Station where, after 20 minutes, they were split up.
The father, who is from a North African background, was questioned about links to radical groups possibly linked to Islamic terrorism. Both he and Daniel were formally placed under investigation.
Daniel's mother then arrived at the station and Daniel was finally released after two hours, but local social services said he was in a 'severely traumatised state after his ordeal.'
A spokesman said: 'He can't sleep and he's crying constantly. He's a terrified little boy. The whole thing has been an absolute nightmare for him.'