More than 30 migrants have been brought ashore at Dover after Border Force vessels intercepted three small boats in the Channel.
The Home Office said the alerts came in the early hours between 04:50 BST and about 06:15 BST.
Thirty-four men and women were passed to immigration officials after undergoing medical checks.
A lifeboat intercepted a fourth small boat carrying a further seven men and one woman on Wednesday afternoon.
The fourth migrant boat, intercepted just after 12:10 BST, was taken to Ramsgate, a Home Office spokeswoman said.
She said the 42 people in total who were brought to the Kent ports gave their nationalities as Afghan, Kuwaiti, Iranian, Iraqi, Yemini, Syrian and Turkish.
On Tuesday, 45 people in four boats attempted to cross the Channel - the world's busiest shipping lane - in thick fog and it is thought one of those groups tried to reach Kent in a small blue and white rowing boat.
A week ago, four migrants tried to cross from France to the UK on a makeshift raft made from two windsurfing boards tied together, using shovels as paddles.
The Home Office said the migrants had left a safe country and, where appropriate, the government would seek to return them.
Minister for immigration compliance Chris Philp said the UK was working with France to tackle the illegal crossings and "bring the ruthless criminals who facilitate them to justice".