Around 400 people are living at Napier Barracks in Folkestone, Kent, where a virus outbreak has added to serious concerns over “nightmare” conditions.
The people living at the barracks have described the situation as “unbearable” and say social distancing is impossible.
There have been reports of suicide attempts and earlier this month many residents went on hunger strike in protest at the conditions, which reportedly include 34 people sharing one shower.
The complex is surrounded by barbed-wire topped fences and hosted Canadian troops in the Second World War.
A petition to shut down the site, along with a similar facility at a barracks in Wales, has amassed more than 10,000 signatures in just two days.
The Home Office, which commandeered the site last year, insists the accommodation in Kent is “safe, suitable, (and) Covid-compliant”.
An open letter to “all British citizens” from an asylum seeker living at Napier Barracks and reportedly signed by more than 200 other residents has been shared by refugee charity Choose Love.
The letter calls out home secretary Priti Patel and immigration minister Chris Philp over conditions at the site.
It says: “We came to this country to save our lives. Lives which were mostly in danger because of war and prosecution.
“Yet we found ourselves in an army camp and we are surrounded by fences and security guards.”
The undated letter says that at least 120 cases of coronavirus have been identified at the barracks with more test results pending – a figure put to the Home Office, which has so far refused to comment.
The letter continues: “We are detained without knowing what we have done to deserve living like this or how long we are going to stay here.
“After so many protests and some suicide attempts, the Home Office still has no intention to improve the situation.
“There are fathers, sons and husbands here. There are nurses, teachers, engineers and talented people here and yet we have been treated like criminals or prisoners.”
Kolbassia Haoussou, lead survivor advocate at the charity, said: “A major crisis is unfolding in these unsanitary and dangerous places. Many of the people trapped here have low immune systems and mental health issues linked to the abuse they have fled.
“The government has the power to end this nightmare now. Empty the barracks, close the camps, save lives.”
Bella Sankey, director of charity Detention Action, echoed calls to shut the barracks “before they are engulfed by tragedy”.
Immigration minister Chris Philp said: “We take the welfare of those in our care extremely seriously and asylum seekers can contact the 24/7 helpline run by Migrant Help if they have any issues.”
Use of Napier Barracks to house asylum seekers was initially authorised for six months under emergency provisions but the Home Office has said it is considering extending its use beyond the current deadline in around March.