At least 28,395 people reached the UK in 2021 – more than triple the figure for 2020, according to PA news agency's figures.
A record number of more than 28,000 migrants crossed the Channel from France to the UK in small boats last year.
The PA news agency reported the figures on Tuesday, based on its analysis of government data.
As people smugglers exploited demand, charging thousands of pounds for trips across the busy shipping lane in flimsy boats, at least 28,395 people reached the UK – more than triple the figure for 2020.
The peak came in November, during the course of which least 6,869 people reached the UK, spurred by favourable weather conditions.
On November 11, a record-breaking 1,185 reached British shores in a single day.
The higher numbers were partly due to the use of bigger boats, carrying an average of about 28 people and sometimes as many as 50.
Such crossings ended tragically for many, with at least 27 migrants drowning off France on November 24 during an attempted crossing in a boat likened by French officials to a children's inflatable pool.
The 27 victims were mostly men but also included seven women, a 16-year-old and a seven-year-old child.
They were mostly Iraqi Kurds but also included an Iranian Kurd, Afghans, Ethiopians, a Somali and an Egyptian.
The high number of migrants crossing to Britain from mainland Europe has become a political headache for British Prime Minister Boris Johnson and his Home Secretary Priti Patel.
The flow of migrants has also soured Britain's relations with France, prompting an unseemly blame game even as both sides try to disrupt the people trafficking networks.
The UK government's Nationality and Borders Bill is currently before parliament, promising tougher action against people smugglers and, controversially, migrants themselves.
If passed, the bill, opposed by rights groups, will allow the return of asylum seekers who have passed through so-called "safe third countries".