The Home Office has been criticised by campaigners after new figures revealed 20 migrants have been held in detention centres for at least two years, according to reports.
One detainee has been in custody awaiting deportation for nearly five years, according to The Independent.
Campaigners and politicians branded the situation a "disgrace" and likened it to Guantanamo Bay.
Jerome Phelps, the director of Detention Action, said: "The US has been widely condemned for detention without trial in Guantanamo, yet the UK stands revealed as locking up migrants for comparable periods in immigration detention centres."
In total, 3,378 people are detained under Immigration Act Powers awaiting deportation, according to figures released to The Independent under the Freedom of Information Act.
They are not facing any criminal allegations and most are failed asylum seekers while others may be those whose visas have run out.
They are housed in detention centres such as Yarl's Wood in Bedfordshire, which has been dogged by reports of sexual misconduct by staff, women being detained for long periods and pregnant detainees being held without justification.
Mr Phelps added: "The Home Office is simply warehousing unwanted migrants, at vast public expense, causing incalculable damage to their mental health."
Shadow home secretary Yvette Cooper said: "It is disgraceful that some people are being detained for over four years."
A Home Office spokesman said: "Those with no right to be in the UK should return home. We will help those who wish to leave voluntarily but will enforce the removal of those who refuse.
"Detention is used as a last resort when an individual will not leave voluntarily or when there is a serious risk they will abscond from bail. When we do detain people it is for the minimum time possible.
"All detention is reviewed on a regular basis to ensure that it only lasts as long as it continues to be justified and necessary. However, we have a duty to protect the public from those who pose a risk of harm and in particular those who have committed serious criminal offences.
"If a court determines that detention has been unlawful, compensation is paid at the end of litigation proceedings. This process can last for several years after the detention has ended."