The first migrants have been detained under the UK’s new “one in, one out” deportation deal with France after crossing the English Channel.
Pictures showed the migrants wearing life jackets disembarking from Border Force boats in Dover on Wednesday, the first day the pilot scheme came into force.
The Home Office said those detained will be held in immigration removal centres until they are returned to France.
Home Secretary Yvette Cooper did not confirm how many migrants were being held and said she was prepared to resist any legal challenges aimed at preventing their removal to France.
She said: “The transfers to immigration removal centres are under way as we speak, so we won’t provide operational details at this point that criminal gangs can simply use and exploit.
“But no-one should be in any doubt: anyone who arrives from now on is eligible for immediate detention and return.”
She said the first migrants could be sent back within weeks.
Cooper added: “It’s the beginning of the pilot and it will build as well over time, but we’re also clear that France is a safe country, so we will robustly defend against any legal challenge that people try.”
The pilot scheme was set up as part of a deal announced by Prime Minister Sir Keir Starmer and French President Emmanuel Macron during his state visit to the UK in July.
Speaking about the first detentions, Sir Keir said: “If you break the law to enter this country, you will face being sent back. When I say I will stop at nothing to secure our borders, I mean it.”
The pilot is set to last 11 months and will see the UK accepting an equal number of asylum seekers who have not tried to cross and can pass security and eligibility checks.
UK officials aim to make referrals for returns to France within three days of a migrant’s arrival by small boat, with French authorities responding within 14 days.
This is in exchange for an approved asylum seeker in France to be brought to the UK under a safe route.
Adults and families in France are able to express an interest in coming to the UK through an online platform set up by the Home Office.
They must meet suitability criteria, go through a standard visa application process and pass security checks.
If accepted, they would be given three months in the UK to claim asylum or apply for a visa, and would be subject to the same rules for all asylum seekers not allowed to work, study or have access to benefits.
The Home Office is expected to launch a campaign in the coming days to make migrants in northern France and elsewhere aware of the new treaty.
As of 30 July, more than 25,000 people had crossed the Channel in small boats in 2025 – about 49% higher than at the same point in 2024.
UK and international law prevents the government from sending asylum seekers back to their country of origin before their claim has been considered and turned down. However, they can be sent to safe countries prepared to consider their claim.
The Conservatives argue that the new scheme will not be a big enough deterrent and will not return large numbers of would-be migrants.
They also believe that Labour’s deal with the French will be less effective than the Rwanda plan proposed by the previous Tory government.
Shadow home secretary Chris Philp told BBC Breakfast that it was a “foolish error” to scrap the scheme which would have seen some migrants sent to Rwanda.