Authorities were called to several incidents which saw 40 migrants including two children, some in dinghies, cross the Channel towards Britain on Christmas Day.
Border Force were involved in five separate instances involving people presenting as Iraqi, Iranian and Afghan, the Home Office said.
A girl was among eight people who arrived in Folkestone, Kent, at around 2.40am.
A child was also one of 13 people on board a dinghy assisted by Border Force off the coast of Deal, Kent, shortly before 7am.
In conjunction with Dover lifeboat and HM Coastguard thirteen casualties were rescued and handed over to partner emergency services and authorities.
— RNLI Walmer (@RNLIWalmer) December 25, 2018
Separately, a Border Force cutter was deployed at 5.50am to the Channel to help a dinghy which was travelling towards the UK with seven men and a woman onboard.
All of those involved underwent a medical assessment and the adults have been transferred to immigration officials to be interviewed.
The children will come under the care of social services, officials said.
In another incident in French waters, nine migrants were rescued and are now in the UK after the engine of the vessel they were travelling in failed.
They have been transferred to the Coastguard to be assessed.
Border Force officials are being assisted by the Maritime and Coastguard Agency after being called to an incident in the Channel before 9.20am involving two people in a small boat travelling towards the UK.
All 40 people are now in the UK, the Home Office said.
A spokeswoman said: "Border Force has intercepted a number of boats containing migrants attempting to cross the Channel overnight and this morning, and has deployed resources to deal with these incidents.
"The evidence shows there is organised criminal gang activity behind illegal migration attempts by small boats across the Channel.
"We are working closely with the French and law enforcement partners to target these gangs, who exploit vulnerable people and put lives at risk."
The Christmas Day crossings follow a number of migrant rescues in recent months involving people trying to travel across the Channel to Britain.