At least 1,185 people arrived on Thursday, the Home Office confirmed.
A record number of migrants have crossed the English Channel in a single day, say UK authorities.
At least 1,185 people reached the UK aboard 33 small boats on Thursday, the Home Office confirmed, surpassing the previous daily high of 853 people.
French authorities said they had also prevented 99 other people from reaching the English coast.
Lifeboat crews and border force boats worked long into the evening after spending hours intercepting boats throughout the day.
The Home Office has labelled the dramatic increase in illegal migrant crossings as "unacceptable".
"The British public is fed up with seeing people dying while ruthless criminal groups profit from their misery," a UK ministry spokesperson said.
Three migrants have been missing since Thursday after attempting the crossing by kayak, according to French authorities.
Their disappearance means four people remain missing in 2021 after attempting to cross the Channel, while at least three others are confirmed to have died this year.
The narrow strait of water can be dangerous for attempted crossings, due to a high density of traffic and strong sea currents.
An estimated 22,000 people have reached the UK in small boats this year, more than double the number in 2020.
Last August, the UK Home Secretary Priti Patel has pledged to "make this route unviable," while the British government has agreed to pay France €62.7 million to increase security on its northern coast.