Over 800 migrants crossed the English Channel to the UK on Saturday – setting a new record for crossings in a single day.
The Home Office said nearly 200 people making the trip were also stopped by the French authorities.
Nearly 12,500 people have made the journey so far this year.
Officials say there are safe and legal routes for migrants and they were working with international partners to tackle the “dangerous crossings”.
The Home Office said the UK authorities rescued or intercepted 828 people in 30 small boats on Saturday, while the French prevented 193 people in 10 boats from reaching Britain.
It said there were no arrivals on Sunday or Monday.
The previous highest number of migrants to cross the Channel in one day was on 12 August, when 592 people made the journey.
Dan O’Mahoney, Clandestine Channel Threat Commander, said: “These dangerous crossings from safe EU countries are completely unnecessary and we are determined to take down the evil criminal gangs behind them.”
A deal agreed between London and Paris last month will see France double the number of police patrolling its beaches. It will also fund improved intelligence sharing and introduce better technology to target people who organise the crossings.
The government hopes an overhaul of asylum rules will deter migrants in future.
The Nationality and Borders Bill, which is currently being considered by MPs, will mean migrants entering without permission could face up to four years in prison.
But it has prompted a backlash from campaigners and charities who have urged the government to create more safe routes and schemes for asylum seekers and refugees.
It comes as ministers announced a resettlement programme to allow 5,000 Afghans to come to the UK, with the long-term goal of helping 20,000 people from the country.
