More than 40,000 have crossed the Channel to so far this year, a new record, the government said on Sunday as it targets a deal with France to fight people smuggling.
The provisional total for this year stands at 40,885, most of them Albanians, Iranians and Afghans – well in excess of last year's 28,561, the Ministry of Defence said.
On Saturday, some 972 people were detected making the perilous crossing in 22 boats, it said.
The figures have been rising for years.
Some 299 were detected making the crossing in 2018; 1,843 in 2019; and 8,466 in 2020, according to the UK.
The numbers have continued to surge despite various UK initiatives including a controversial plan to send the migrants to Rwanda, which has been blocked in the courts.
Last week, British Prime Minister Rishi Sunak said a new plan agreed with France was in the works, after his first face-to-face meeting with President Emmanuel Macron.
In talks on Friday, French Foreign Minister Catherine Colonna and British counterpart James Cleverly "stressed the urgency of tackling all forms of illegal migration including small boat crossings and addressing their root causes", according to a joint statement.
The rising numbers have caused a logjam in asylum claims and increased accommodation costs estimated by the UK government at £6.8 million ($7.8 million) a day, straining local services and fuelling public anger.
Writing in newspaper The Sunday Telegraph, Immigration Minister Robert Jenrick said Britain's "generosity" was being "abused" by economic migrants who were "asylum shopping" their way around Europe.
"'Hotel Britain' must end and be replaced with simple, functional accommodation that does not create an additional pull factor," he added.
The government is looking at alternatives to hotel rooms for asylum claimants including disused student accommodation, defunct holiday parks and even budget cruise ships, according to The Sunday Telegraph.
But refugee rights groups accuse the government of a callous and chaotic approach, after unsanitary conditions developed at one overcrowded asylum processing centre in Manston, southeast England.
Migrants at the facility are being vaccinated against diphtheria due to a rise in cases of the highly contagious disease, officials said.
But Jenrick said a closer relationship with France would help to deter those "attempting to cheat the process".
The new partnership will reportedly see Britain pay about £80 million ($95 million) on beefed-up technology and measures such as joint operations against people-trafficking gangs.