However, it is understood that there is unlikely to be a comprehensive judicial review challenge to the entire policy, which was what proved successful in grounding the first Rwanda flight.
Starmer is expected to claim the high-profile return of migrants to France is a significant moment in efforts to tackle the small-boats crisis after a fortnight that saw his phase two reset overshadowed by the twin scandals of United States ambassador Lord Peter Mandelson and Angela Rayner, the former deputy prime minister.
Although the initial numbers returned in the pilot scheme are small, both Starmer and Shabana Mahmood, the new Home Secretary, want to scale it up to act as a deterrent to show migrants seeking to make the dangerous crossing that it is not worthwhile.
More than 31,000 migrants have crossed the Channel this year, 40% higher than at the same point last year and the highest number since the first arrivals in 2018.
Since Labour took power, more than 50,000 have reached the UK. Four migrants including two children died last week attempting the perilous crossing.
The first flights – believed to be scheduled for Monday, Tuesday, Wednesday, and Friday on Air France – will come ahead of United States President Donald Trump’s arrival in the UK on his state visit.
Government sources confirmed the flights will start this week.
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.”
‘Morally repugnant’
The first group to be detained were among the 155 migrants who arrived in two dinghies on August 7, the first crossings since the deal with France came into effect.
They were taken to the Home Office processing centre in Manston, Kent, where Border Force officers selected adults who will be the first to be removed to France.
After being taken into custody, they were transported to Harmondsworth, one of the seven immigration removal centres in the UK, by Mitie Care and Custody, the Home Office’s private contractor that runs most of the detention centres and supplies immigration escorts.
The UK then had to inform France within three days which individuals it intended to return, with the French then due to respond within a fortnight with any objections.
The migrants detained were given access to lawyers and had seven days to register an appeal against their removal.
Refugee charities condemned the “morally repugnant” detention of migrants due for deportation and said the scheme “must be challenged”.
According to refugee sources, the emerging picture seems to indicate that those selected come from nationalities that have previously received high grant rates of refugee status but also account for significant numbers of Channel migrants. The countries include Eritrea, Afghanistan, and Sudan.
The 100 or so to be returned are small in comparison with the average of about 800 people who have crossed each week so far this year.
There are concerns that smugglers will exploit the small proportion of returns as an advertising technique by pointing out the slim chance of being deported.
In an attempt to counter it, the Home Office last week launched an advertising campaign in France to warn migrants about the prospect of being returned if they crossed.
An online portal on which asylum-seekers in France can register their interest in benefiting from the scheme opened last month.
To qualify, asylum-seekers must meet certain criteria: they must be in France at the time of applying, have a family connection in the UK and be from a country with a high asylum grant rate, such as Eritrea, Somalia or Afghanistan.
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