The latest figures show that over 3,600 migrants arrived in Britain through the Channel between July and September last year.
The figures published in a report by Chief Inspector of Prisons Peter Clarke. He said that hundreds of asylum seekers who made it across the Channel in the early autumn were detained in “wholly unacceptable” conditions in a freight shed with nowhere to sleep other than a concrete floor.
“Those who left the insanitary makeshift camps near Calais and made it through the Channel tunnel under lorries and freight trains were held in a lorry bay in Folkestone, Kent, with no clothing, food or hot drinks provided," he added.
Clarke noted that there were 381 children among the individuals detained at centers in Dover and Folkestone.
“It was clear that the unprecedentedly high number of people arriving from France had led to a strain on the infrastructure,” he said.
The unexpected increase in migrants and refugees clandestinely entering the UK through the Channel from June last year included significant numbers from the Middle East and North Africa particularly Eritrea, Sudan and Syria.
The asylum seekers were trying to enter Britain without being detected, either hidden in vehicles on the ferries to Dover, in the Channel tunnel or on freight trains arriving in Folkestone.
Border security in Calais has been increased by the deployment of 1,300 French police officers and extra fencing and security guards.