The UK government plans to reform the asylum system but the British Red Cross charity warns that a two-tier system risks being created that would see anyone arriving via a third country being held in reception centres, potentially for months.
Asylum seekers have to live in dirty and unsafe accommodation for lengthy periods while their claims are processed, according to the latest report on Britain's treatment of migrants.
The British Red Cross tells of accommodation so ramshackle that a roof collapsed and how migrants were forced to wear filthy clothing to keep warm.
The report follows a warning last week from the Refugee Council that asylum seekers face food shortages and racism in UK hotels, with one teenage boy needing hospital treatment because of the poor food provided.
The Red Cross report was based on the accounts of 100 people that the charity supports in asylum accommodation. It found that requests for medical help were ignored and staff searched belongings without permission.
"We are very concerned about the living conditions asylum seekers are facing as they wait months for their applications to be processed," said Mike Adamson, the charity's chief executive.
"We believe that people who have experienced some of the worst horror imaginable - fleeing war, persecution and violence - should be able to expect a safe, clean place of refuge when they arrive in the UK.”
The charity urged the government to work with charities and other bodies to find more housing in communities for new arrivals. “This is a once-in-a-generation opportunity to create a fair and effective approach to asylum, in line with British values of kindness and compassion,” said Mr Adamson.
The coronavirus pandemic led to a halt in evictions from accommodation for people who had received decisions on asylum claims.
It created a logjam with 64,000 in the system by the end of 2020, compared with the normal level of about 50,000. New arrivals have been sent to re-purposed military barracks and hotels to cover the shortage of suitable accommodation.
The Red Cross called for an immediate end to the use of military barracks as asylum accommodation.
A Home Office spokeswoman said: "We reject these claims. We always take the wellbeing of all those in the asylum system seriously.
"Our new plan for immigration will reform the broken asylum system. We will welcome people through safe and legal routes, while preventing abuse and reducing the pressures on the system created by parallel illegal routes."