In Cardiff Prison, in south Wales, 30 asylum seekers have been refusing food for over a week in protest at their conditions.
Very little is publicly known about where they come from, their names or whether they arrived in Britain seeking better employment or were fleeing persecution.
But as more and more asylum seekers detained in prisons in Liverpool and Kent protest against their imprisonment, civil rights groups are urging the British government to end the practice.
The detainees in Cardiff began refusing prison food last Wednesday, but have access to food from the prison shop and are drinking liquids.
A recent medical examination found there was no cause for concern, but the Refugee Council's deputy director, Ms Margaret Lally, said yesterday that detaining asylum seekers who had not been charged or convicted of a crime was "grossly unjust" and must end.
"Asylum seekers are being forced into prison regimes when they have neither committed nor even been accused of a crime. Many of the processes, such as handcuffing in public and denial of fresh air, are inhumane and degrading to people who have fled unjust imprisonment, torture and persecution," she said.
About 500 asylum seekers and those who have violated immigration policy are held in prisons in Britain and they come from countries such as Algeria, Angola, Zaire, India and the Ukraine.
The Prison Service yesterday said the system of detaining asylum seekers in prisons and detention centres mainly involved people whose applications for refugee status had been refused and where there was a risk they could abscond.
But the British government has said it recognises that detaining asylum seekers in prisons is "far from ideal" and in addition to existing facilities, two purpose-built secure centres are expected to begin taking in asylum seekers in Scotland and the south of England later this year.
Civil rights groups have also condemned officials for detaining asylum seekers with convicted criminals.
The Home Office acknowledges that in some situations, asylum seekers may be mixing with convicted prisoners for short periods of time during the day within the prison system.
Most detainees live in remand conditions where they are not mixing with convicted prisoners, but some of those held within the prison system can mix with other prisoners during times of association.
This happens even though the asylum seekers have not been charged or convicted of any crime whatsoever.
John O (not his real name), a spokesman for the National Coalition of Anti-Deportation Campaigns, said some asylum seekers can be detained almost immediately upon arrival in Britain, separated from their families and sent to detention centres or prisons while their claims are processed. Some may be at the beginning of the asylum application process, but he accepts that most detainees are at the appeal stage.
However, several detainees have told his organisation about the difficulties of living within the prison system.
"The detainees tell us about the conditions they are living in, that they live, eat and sleep in the same room with the toilet.
They are locked up 23 hours a day and allowed one shower a week. They also say they are forced to wear prison uniforms, although if you speak to the governor he will say that they have a choice," John O said.
Amnesty International is also concerned about the British government's process of detaining asylum seekers.
It says there is no proper legal oversight of the practice and a lack of sufficient segregation between asylum seekers and convicted criminals.
A spokesman for Amnesty insisted asylum seekers should not be treated as if they were convicted criminals: "Is the government saying they present a greater risk to society than convicted criminals for whom there is no place in prisons?"