The Home Office says 616 people crossed the Channel on Sunday – the highest daily number this year.
More than 600 migrants crossed the English Channel on Sunday, the highest number on a single day so far this year, the Home Office said.
Some 616 people were detected making the journey from France in twelve small boats.
The previous daily high for this year was 497 people on April 22.
The total number of migrants making the journey this year is more than 8,000, which is about 2,000 less than at the same point last year.
Speaking in Dover last week, Prime Minister Rishi Sunak said his plan to cut the number of migrants crossing the Channel in boats was working and numbers were down for the first time.
Mr Sunak told BBC political editor Chris Mason that crossings to the UK were down by a fifth, and figures for Albanians heading to Britain were down by 90%.
At this point last year, the cumulative figure had just passed 10,000. The total number of crossings last year was 45,755.
Mr Sunak has made reducing the number of Channel crossings a key part of his premiership, including via the Illegal Migration Bill.
The plans would mean anyone reaching the UK without permission would be detained and promptly deported, either to their home country or a third country such as Rwanda.
The bill would create broad new detention and search powers, and migrants would be barred from claiming asylum. It would apply even if a person claims to be a victim of trafficking or modern slavery.
It has been heavily criticised by some campaigners, and the Joint Committee on Human Rights – which is made up of MPs and peers – said earlier this week it would breach a “number of the UK’s human rights obligations”.
While the bill has already passed in the Commons, it was strongly criticised on Monday in the House of Lords during a debate which ran into the early hours of Tuesday morning.
Liberal Democrat Baroness Ludford said peers had been “abused, bullied and intimidated” by the government over the plans.
But Mr Sunak and government ministers say the tough measures are necessary to prevent people smuggling networks from profiteering from the dangerous Channel route.
Responding to Monday’s crossings, a No 10 spokesperson said: “There is a great deal of work going on which is stopping these criminal gangs in their tracks.
“But, clearly, crossings are continuing and that is because we have not been able to put in place our full plans; and obviously there is a great deal of work across government to that end.”
Labour’s shadow immigration minister Stephen Kinnock said the PM “needs to roll up his sleeves and start doing the hard graft, rather than ploughing on with the headline-chasing, government-by-gimmick approach”.
Additional reporting by Sean Seddon