The first deportation flights under a new UK–France "one in, one out" returns agreement are expected to take place imminently, the Home Office said, as Conservative opponents warned the scheme would be overwhelmed by last-minute legal challenges.

The treaty, which came into effect on Aug. 7, allows people who cross the English Channel in small boats to be detained and removed to France. Since the agreement began, 5,435 small‑boat arrivals have reached Britain, the notes show, and Home Office sources said they expected the initial returns to occur this week.

Officials said some people who arrived in early August were detained at immigration removal centres and that an undisclosed number had been issued formal removal directions. A Home Office spokesman said: "Under the new UK–France treaty, people crossing in small boats can now be detained and removed to France. We expect the first returns to take place imminently. Protecting the UK border is our top priority. We will do whatever it takes to restore order to secure our borders."

Shadow Home Secretary Chris Philp, a former immigration minister, cautioned that the removals would be subject to "a slew of last‑minute legal challenges" from migrants and their representatives seeking to block flights. Philp said the government had not removed the Human Rights Act for immigration matters and that claims, including modern slavery assertions, would complicate attempts to effect removals.

"In any case, removing a tiny handful of people will have no deterrent effect," Philp added, noting recent crossing figures. Records show 1,097 migrants reached Britain on Sept. 6 and a further 927 arrived the following week, though crossings were briefly reduced by strong Channel winds.

The pilot arrangement foresees a limited exchange: migrants who entered the UK illegally across the Channel can be returned to France, while others in France will be flown to the UK and issued a visa of up to three months while their asylum claims are considered. Government sources have suggested the scheme could see around 50 people sent back each week, a rate that would return fewer than 2,000 people before the agreement expires on June 11 next year.

Critics have said the scale of the pilot is small relative to the number of crossings. So far this year, 31,026 people have arrived in the UK by small boat, an increase of about 38 percent on the same period last year.

The Conservatives pointed to legal precedent in which attempts by the previous government to remove asylum seekers under the separate Rwanda scheme were halted by a late injunction from the European Court of Human Rights in June 2022. Ministers insist the new bilateral treaty with France includes mechanisms for detention and removal that will withstand legal scrutiny, and Home Office officials said rigorous security checks would be carried out on migrants coming to the UK from France. The French authorities, however, will not provide personal details of migrants transferred to Britain, officials said.

The UK taxpayer will fund both sides of the one‑for‑one arrangement, ministers have acknowledged. Labour prime minister Keir Starmer and French president Emmanuel Macron announced the agreement in July; Starmer said at the time that people who break the law to enter the country would face being sent back. Opponents called some government claims about the scheme's deterrent effect "grossly exaggerated."

As the first removals are prepared, officials said selection for return will be limited and subject to individual legal and welfare assessments. Legal groups and charities have said they will continue to advise and represent migrants facing removal, and ministers face scrutiny over how the scheme operates in practice once flights begin.