Small boats carrying 284 people were intercepted trying to cross the Channel on Tuesday.
Border Force officials stopped eight boats, while French authorities intercepted one crossing carrying a further 20 migrants.
So far this year more than 9,700 people have reached the UK in dinghies.
The Home Office has called the crossings "dangerous" and said those without a legal right to remain in the UK would be returned home.
Dan O'Mahoney, clandestine channel threat commander, said there has been a rise in small boat crossings due to "a surge in illegal migration across Europe".
He said: "We have signed a strengthened agreement with our French counterparts to increase police patrols on French beaches and enhance intelligence sharing.
"The government continues to take steps to tackle the unacceptable problem of illegal migration through the Nationality & Borders Bill which will protect lives and break this cycle of illegal crossings."