LONDON: More than half a billion pounds has been spent on immigration detention in four years, figures show, prompting renewed calls for a limit on length of time immigrants can be held in removal centres.

The government shelled out £523.5 million on detaining people for immigration reasons between April 2013 and March 2017, with an additional £16.2 million spent on damages awarded to immigrants who were detained unlawfully in the same period.

The figures, revealed in response to a written question by the Liberal Democrats, have led to renewed criticism of Britain for being the only EU country without a statutory time limit for the detention of immigrants, with Tory MPs and lawyers now calling on ministers to impose a strict 28-day limit.

Immigration detention is the practice of holding people who are subject to immigration control while they wait for permission to enter or before they are deported or removed from the country. It is an administrative process, not a criminal procedure, and is the decision of an immigration official, not a court or a judge.

The practice has been blamed for inflicting mental breakdowns on people charged with no crime and given no release date, with last year seeing six people die in detention – the highest annual count on record. Survivors of torture, trafficking and rape are among the tens of thousands held in overcrowded centres.

In the year ending September 2017, 27,565 people entered detention in the UK. Of those who left detention in the year ending June 2017, more than a quarter (28 per cent) were there for between 29 days and four months and 1,943 were detained for more more than four months – of whom 172 had been in detention for between one and two years.

Twenty-eight were held for two years or longer. As of 30 June 2017, the longest length of time a person had been detained for was 1,514 days.

A significant number of immigration detainees are wrongly detained, with £21 million paid out over the past five years in damages awarded for unlawful detentions, as revealed last month in response to a written question by Tory MP Andrew Mitchell.

Politicians, lawyers and campaigners are now urging the government to impose a strict 28-day limit on immigration detention, with an upcoming immigration bill offering a fresh opportunity for MPs to do so.