The Office for National Statistics said a recovery of travel following COVID-19, and an increase in arrivals of international students who had been studying remotely during the pandemic had contributed to the rise.

An estimated 1.1 million long-term immigrants arrived in the year to June, an increase in 435,000 on the previous year. The biggest proportion of those leaving Britain were EU nationals.

Three new visa schemes — for Ukrainians fleeing the war, the resettlement of Afghan nationals and a route for Hong Kong British nationals — together added around 186,000 to the number of arrivals, the ONS said.

“A series of world events have impacted international migration patterns in the 12 months to June 2022. Taken together these were unprecedented,” Jay Lindop, director of the ONS Center for International Migration, said.

Migration levels have been in the headlines again in Britain in recent weeks as some business leaders called on the government to liberalize immigration to help boost growth. That has been rejected by Prime Minister Rishi Sunak who, on Monday, emphasized instead the need to tackle illegal immigration.

Sunak and Home Secretary Suella Braverman have also come under pressure to do more to stop illegal migrants making perilous journeys across the Channel, with the government criticized for conditions at an overcrowded processing center in southern England and a firebomb attack on a similar site nearby.

Earlier this month, Britain signed an agreement with France to ramp up efforts to stop migrants crossing the Channel.

Figures released by the government on Thursday showed 33,029 people were detected arriving by small boats across the Channel between January and September this year, with 61% of those people arriving over the summer in the months July to September.

The month of August saw the highest number of small boat arrivals of any month since data has been collected, it said.