People have begun arriving at a military barracks in Kent which is being used to house migrants.
The first of up to 400 asylum seekers were seen at Napier Barracks in Folkestone on Monday evening.
The arrivals are understood to be migrants who crossed the Channel aboard small boats.
The Home Office is using the space as "contingency accommodation", but Folkestone and Hythe MP Damian Collins said the arrangement needed clarifying.
"They're saying they're going to be providing appropriate security but we're not really sure what that will be," Mr Collins said.
"We're assuming people will be able to come and go freely from the barracks, so there's a question of the impact on the rest of the local community."
This summer has seen a huge influx of migrants crossing the English Channel.
More than 6,000 have made the journey so far this year and September is a record month with about 1,500 making the crossing.
The Home Office said using the barracks would ease its reliance on hotels and provide savings of up to 50% for the taxpayer.
Napier Barracks, one of several at the Shorncliffe Army Camp, was selected to house migrants while their asylum claims are processed.
It is understood a military barracks in Wales is also being considered for housing migrants.
Any military training will be relocated to alternative sites or rescheduled, so there will no military personnel on site.