Many are detained or imprisoned for months - one was held for 17 months - without being told why and without any chance to put their case to a court or tribunal. About 600 asylum-seekers are in detention.
The effect of custody on people who are already fearful for themselves and their families is devastating, the reports say. Three of the 50 people seeking refugee status, who were the subjects of a report by Amnesty International, tried to commit suicide. Three others, not part of the report, have killed themselves.
Of the 47 asylum-seekers who were the subjects of the other report, by the Medical Foundation for the Care of Victims of Torture, two had tried to hang themselves and eight needed psychiatric care.
Amnesty concluded that in each of the 50 cases there had been breaches of human rights legislation or internationally agreed standards. None of the asylum-seekers had been properly informed why they were being detained. In 31 cases, there was no independent review. More than half were held in jails for criminals and the average length of their detention was 154 days - almost three times as long as criminals on remand awaiting trial.
Yesterday, a Home Office spokeswoman said: 'We take our obligation to genuine refugees very seriously and we do not accept that our legislation is in breach of international conventions on human rights.' But Amnesty challenged her assertion that detention was used only as a last resort. It said nearly half the people in the study were eventually granted asylum or released and given temporary leave to remain in the country - but only after months of detention.
Richard Dunstan, Amnesty's refugee officer, who carried out the study, said that in most cases he could find no differences between the circumstances of the refugees who were locked up and of those who were not. This heightened Amnesty's view that decisions to lock asylum-seekers up were arbitrary.
Mr Dunstan said. 'We don't have a criminal justice system whereby police officers can send people to prison without telling them why or allowing them to go before a court, so why do we have such a system for refugees?'
Amnesty and the Medical Foundation called on the Government to introduce safeguards to ensure asylum-seekers were held only as a last resort. They include removing the power to detain from immigration officers, ensuring that refugees are notified in writing of reasons for detention, the right to legal advice, and an oral review within seven days.
Prisoners Without a Voice; Amnesty International, 99-119 Roseberry Avenue, London EC1R 4RE; pounds 6.99.
A Betrayal of Hope and Trust; Medical Foundation for Care of Victims of Torture, 96-98 Grafton Road, London NW5 3EJ.