A 28-day time limit on immigration detention could save the public purse up to £35m a year, a report by economic data consultants has found, prompting renewed calls for ministers to bring an end to the indefinite jailing of suspected illegal immigrants.
The UK has one of the largest immigration detention systems in Europe and is the only country in the region without a statutory time limit on length of detention.
The human rights group Liberty commissioned Cambridge Econometrics to examine the costs of jailing suspected illegal immigrants and the potential savings that could be achieved by introducing a 28-day cap on detention.
The report, which has been sent to the Home Office and seen by the Guardian, concludes that after taking into account the costs of potential alternatives to detention, such as community support projects, the government could save the taxpayer between £25m and £35m.
Sam Grant, the policy and campaigns manager at Liberty, said: “Locking people up with no release date always has a devastating human cost – now we know it has a financial cost, too. This report shows the government has a clear opportunity to create a cheaper, more humane system by introducing a 28-day time limit.
“This win-win policy would save the taxpayer tens of millions of pounds while making sure fewer people are detained and for shorter amounts of time. It’s time the government listened to growing pressure from the public and all political parties and ends indefinite detention.”
There have long been calls for a cap to be introduced on immigration detention. Most recently, the home affairs select committee, chaired by Labour’s Yvette Cooper, said the Home Office’s approach to immigration detention was careless and cavalier and called for a 28-day time limit.
Last July, in a statement to parliament following the publication of a report by the former prisons and probation ombudsman Stephen Shaw into conditions in immigration detention centres, the home secretary, Sajid Javid, said he would review how time-limited detention worked in other countries to better inform the debate in the UK.
In 2017-18, Home Office expenditure on detention was £108m. Under a 28-day immigration detention time limit, Cambridge Econometrics found there were potential long-term cost savings of £55m to £65m a year.
The report said plausible alternatives cost less than detention, with an estimated cost range of £6m to £30m.
In 2018, about 25,000 people entered detention and a similar number left, lower than the historical trend.
Between 2010 and 2017, the number of people entering and leaving detention ranged from 26,000 to 30,000 each year, with the exception of 2015, when this climbed to 32,400 entering detention and 33,200 leaving.
On average, about 65% of people detained are released within 28 days, the report said, while 95% are released within six months and 99% within a year.
The 2018 figures show a possible departure from this trend, with a higher proportion of people released within 28 days, 69%.
However, Home Office statistics going back to 2010 also show individual cases of people being held for much longer, including more than four years in some instances. In addition, many people can also face multiple stints of detention and redetention, which is not reflected in Home Office statistics.
Detainees are held in eight detention centres and two short-term holding facilities. Eight are in England, one in Scotland and one in Northern Ireland.
A Home Office spokesperson said: “There has been much debate about the introduction of a 28-day time limit, but as Stephen Shaw noted, it rests mainly on slogans rather than evidence. This is why the home secretary commissioned an internal review of how time limits work in other countries and how they relate to any other protections within the detention systems in these countries.
“No one is detained indefinitely. Most people detained under immigration powers spend only short periods in detention. In 2018, 92% of those detained were removed or released from detention within four months, and 69% in less than 29 days.”