Brook House was opened in March and can house 426 people
A demonstration has been held over plans to turn a four-star hotel at Gatwick Airport into a immigration detention centre.
Arora Management Services has applied for permission to convert the 254-room Mercure Hotel near the airport's north terminal into a secure removal unit.
Campaign group No Borders held a protest inside one of the firm's other hotels, near Heathrow, on Tuesday.
There are currently two immigration detention centres near Gatwick.
Arora Management Services submitted a change of use application to Crawley Borough Council last month.
The owners of the hotel said the current economic climate had caused them to look at a variety of options for a number of their buildings.
It said one option was to turn the Mercure hotel into a detention centre but the planning application it had submitted to Crawley council was "speculative".
Rosie Young, of No Borders, said: "I think it is a pretty sick idea really to turn a place which is supposed to be a place for visitors to come into a removal centre.
"Obviously it's very profitable to have a visitors here that can't leave because they are not allow to leave."
The Home Office said it had no plans to open a third removal unit near Gatwick Airport.
Rosy Young, of No Borders, said a third "prison for migrants" was not needed