The majority of people detained after crossing the Channel to the UK in recent years have been referred as potential victims of modern slavery.
Almost all of those who came under the National Referral Mechanism (NRM) while awaiting their return from the UK were subsequently released from detention, the Home Office said.
Research published by the department on Tuesday said that, where people were detained for return having crossed the Channel in 2021, almost three-quarters were referred under the NRM – a system which identifies potential victims of modern slavery and human trafficking so their case can be considered.
For the period between January and September 2022 it was lower, at two-thirds.
Under the process, potential survivors are expected to be given an initial decision such as this on their case within five working days, and a “conclusive grounds” decision as soon as possible thereafter.
The Home Office said most people in its analysis are yet to receive a final decision.
Up to 2021, at least 80% of people were released proactively by the Home Office, the research said, but in 2022 more than half were granted bail by an immigration judge.
The Home Office said that, where people were not detained for return from the UK, the percentage of people who arrived in 2021 being referred to the NRM within three months was less than 3%.
It soared from 6% of detentions in 2019 involving a referral to 53% in 2020 and 73% in 2021.
Of the 1,305 people detained for return having crossed the Channel between January and September 2022, 842 were referred to the NRM and 780 received a positive “reasonable grounds” decision.
This was up from 831 detained in 2019, 50 of whom were referred to the NRM and 36 given a positive initial decision.
The referral rate has since fallen slightly, the Home Office said, to 65% for detentions ending between January and September 2022.
The latest overall figures for modern slavery published last week showed 16,938 potential victims were referred to the Home Office in 2022 – the highest annual number since the NRM began in 2009.
This rose by a third (33%) compared with the previous year, which saw 12,706 potential victims referred.
The Government said more referrals from first responders have driven the increase and that it could be linked to the rise in detections at the border, particularly the large rise in Channel crossings.