Britain's border authorities intercepted a number of small boats containing a total of 40 migrants who attempted to cross the English Channel overnight and in the morning of December 25.
A further three men were detained in the early hours of December 26, the UK Home Office confirmed to Euronews.
The ministerial department said it deployed resources to "deal with these incidents" and added that evidence suggested organised criminal gang activity was behind the migration attempts.
“We are working closely with the French and law enforcement partners to target these gangs, who exploit vulnerable people and put lives at risk," a Home Office spokesperson said.
In the early hours of Wednesday, December 26 "Border Force was made aware that three adult male migrants on board a small boat, who presented themselves as Iranian, had been rescued by the French authorities near Dover," the department said.
Before this, the Home office confirmed 40 migrants crossed the Channel on December 25 and were in the UK. There were a total of five incidents overnight, it added.
Migrants included two children and people who claimed to be Iraqi, Iranian and Afghan nationals.
In one incident, off the coast of Deal, Kent — authorities intercepted a dinghy with 13 on board.
Another group of eight migrants arrived in Folkestone and a Border Force cutter was deployed to assist a further dinghy in the Channel with eight people on board.
The Home Office said its authorities also assisted French maritime officials in an incident off the coast of France involving a vessel which turned back after an engine failure, with nine people on board.
The Border Force was made aware of a final incident at 9.20 am on Tuesday, a small boat with two onboard travelling towards the UK.
All 43 migrants underwent a medical assessment. The adults have been transferred to immigration officials to be interviewed and the two minors have been transferred to social services, the Home Office said.