By Kate Smith

They are like ghosts, moved without warning or explanation across the country in the dead of night, transported in unmarked vans. A silent cargo, often handcuffed, frozen by fear and unable to make a call or let their family know what is happening to them.

"Ghosting" happens most nights as detainees at removal and detention centres are taken from their families and driven, sometimes more than 500 miles, the Sunday Herald has been told.

Staff claim Dungavel is at crisis point, with overcrowding at up to 150% and chronic staff shortages which often leave inadequate cover for "suicide watch", according to sources. Five to 10 families with children are detained there at any one time, detainees claimed.

Each night the detainees, including young children, fear that they will be taken from their beds, not knowing if their destination will be another UK removal centre or an airport.

According to sources, ghosting is an increasingly common practice endured by up to 80% of detainees at detention and removal centres in the UK.

For the first time a true picture of life inside Dungavel has emerged as a detainee spoke about the daily routine at Scotland's only removal centre.

"They move people all the time in the middle of the night. I live in complete fear," said Charles Nahimana, 40, from Burundi, who was taken from his Glasgow home in February.

"At the headcount each morning there are new people who weren't here the previous night. Most rooms have four beds and you wake up when they come for two, maybe three of your room mates in the middle of the night.

"You wake up again when they bring the new people in. Some have been picked up from their homes but most of them moved from other detention centres. I sleep in fear. If you hear a noise at your door at night you are immediately wide awake and your first thought is they have come for me'. People who have been spirited away like this tell me they don't tell you what is happening. They take you and you have to switch your phone off and you can't tell anybody what is happening."

As he speaks Nahimana looks over his shoulder and holds his phone. It is his lifeline to the outside world.

He picks up his bible which has his children's names in it. "I couldn't send my two-year-old daughter a birthday card," he adds. "I knew I couldn't send a present but it was very distressing not to be able to even send a card.

"We are in a worse position than prisoners. If you were in prison you would have a sentence and know how long you were to be detained for. You would have certain rights. This is psychologically and emotionally very distressing."

The tall and graceful former charity volunteer has lived in Britain for six years after he fled persecution. Two of his children were born in Glasgow and know no other world. He displays his son's school report which shows straight As.

One removal centre employee told the Sunday Herald that many removal centres are at over 150% capacity. "I would estimate that they move around 70%-80% of detainees at night time. I have seen families arrive who are totally physically exhausted and devastated. They have been kept up all night. Sometimes they are transported long distances in the police cells in the van. These are basically cages inside the vans. They are sometimes handcuffed.

"But the main reason why they transport so many at night is that, unless they are in a police cell in the van, the detainees are often hammering on the sides and shouting and if it was daytime, imagine the outcry if a van like that pulled up at the traffic lights."

John Watson of Amnesty International in Scotland said: "We are justifiably concerned about detention limits of 42 days but these are people in our society detained without limit.

"This kind of activity increases the discomfort and distress of these innocent people who should be treated with dignity. I can't see that driving people around at night is treating them with dignity. None of the reasons given justifies the practice of people getting moved at night. Also, families are only meant to be detained as a last resort but our research is that it is not a last resort."

John Wilkes, chief executive of the Scottish Refugee Council, said: "Holding children in the back of a van for eight hours or more, sometimes with no breaks or access to food or water, transporting them and their parents far away from their lawyers and community networks, is traumatic and inhumane at any time of the day."

The UK Border Agency refused to answer questions. A spokesperson said: "All Immigration Removal Centres are operated in line with strict rules and are regularly inspected. Detention plays a vital role in maintaining an effective immigration control, including the removal of those without any right to remain here and who refuse to leave the UK voluntarily."

Although immigration and asylum are reserved matters, a spokesman for the Scottish government said: "We have made clear our concerns about the operation of the UK asylum system in Scotland and the treatment of asylum seekers in general. We remain fundamentally opposed to dawn raids, to the forcible removal of children and to the detention of children at Dungavel."