The British government agency that oversees immigration said nine men, two women and a 10-year-old child were in the group, who reported being Iranian. The people received health checks and were turned over to immigration officials for interviews, the Home Office said.
A surge of Channel crossings in recent weeks prompted Home Secretary Sajid Javid to call a crisis meeting with top officials from Britain's Border Force and National Crime Agency and senior government officials.
Javid said afterward that the government planned to put two more Border Force ships on patrol in the English Channel to protect both the lives of migrants making the risky journey and Britain's borders.
About 230 migrants tried to traverse the water from northern France to southern England in December, he said. "We must remember that this is one of the most treacherous stretches of water that there is, 21 miles with people taking grave risk," Javid said.
He said two Border Force cutters would be called back from abroad to join a third already stationed in the Channel. Matthew Saltmarsh, a spokesman for the U.N. Refugee Agency, said U.N. officials also are worried about an upturn in risky crossings by migrants.
"The increase in attempted crossings of the Channel to the UK from France since autumn is a real concern," he said in an email. "The winter conditions and use of flimsy vessels present significant dangers to asylum seekers attempting the crossing."
British and French officials have been discussing increasing patrols of the waterway that separates their countries and connects the North Sea to the Atlantic Ocean. The narrow Channel's length is 563 kilometers (350 miles), but navigating it can be dangerous for passengers in the small boats typically used for ferrying migrants because of heavy shipping traffic.