Border Force officers today detained more than 400 migrants in British waters in what is a single-day record.
A total of 409 people in 27 boats were taken in by security forces.
More incidents are thought to be ongoing, meaning the daily total is likely higher.
No details about their genders, nationalities or ages have been given.
The Home Office said tonight: “Border Force have dealt with 27 incidents so far today involving 409 people.
“Further incidents are ongoing and information will be provided in due course.”
The previous single-day record, on August 6, saw 235 people arrive in 17 vessels.
Dozens of the refugees were pictured looking exhausted after crossing the Channel in perfect conditions today.
The clear blue skies and calm waters are likely to have encouraged people to attempt the crossing.
At least eight dinghies dodged Border Force boats to make it to shore in Kent today.
One woman was seen lying on concrete steps in sodden clothes complaining about stomach pains.
A group of people seen walking up a hill after landing at St Margaret's at Cliffe near Dover today, with around 25 rounded up in the area and detained.
The huge rescue operation has been underway since at least 2am today and has involved the Coastguard, Border Force, plus lifeboats from Dover, Dungeness and Walmer.
Dover lifeboat was seen bringing 25 people into the town's port this morning - and it was later carrying around 13 to shore around 10am.
A Coastguard spokeswoman said today: "Today we have been assisting Border Force with incidents off Dover.
"HM Coastguard is committed to safeguarding life around the seas and coastal areas of this country.
"We are only concerned with preservation of life, rescuing those in trouble and bringing them safely back to shore, where they will be handed over to the relevant partner emergency services or authorities."
So far this year, at least 5,025 migrants have arrived in small boats - including a single-month record of 1,468 in August.
In 2019, some 677,000 people moved to the UK as long-term immigrants, for reasons such as work or study.
French authorities say they have stopped five times more crossings in the first six months of this year than last year.