Almost 50 migrants were detained in Britain after crossing the English Channel at the weekend.
Twenty people were found on Saturday after a small boat arrived in the county of Kent. A Border Force cutter then intercepted another small boat carrying 11 men.
Three adults and three children were found by police in Sussex after arriving in a small craft.
And about midday, eight men and two women were picked up from another boat travelling across the Channel, the British Home Office said.
All 47 migrants said they were Iraqi and Iranian nationals.
The adults were medically assessed before being interviewed by immigration officials, the British Home Office said. The children were taken into the care of social services.
"Anyone crossing the Channel in a small boat is taking a huge risk with their life and the lives of their children," a Home Office spokesman said.
"Since December, two cutters have returned to UK waters from overseas operations, we have agreed to a joint action plan with France and increased activity out of the Joint Co-ordination and Information Centre in Calais.
"It is an established principle that those in need of protection should claim asylum in the first safe country they reach and since January more than 50 people who arrived illegally in the UK on small boats have been returned to Europe."
In two days last month, more than 40 undocumented immigrants were detained by border officials in Kent after crossing the Channel.
In June, then home secretary Sajid Javid said France was considering night-time drone flights on its northern coast to tackle people-smuggling networks.
At least 976 people, including about 89 children, have crossed the Channel in small boats since November 3, 2018.
