A small boat loaded with migrants heading for British shores from France capsized in the freezing waters of the English Channel early on Wednesday, resulting in four deaths, the British government said.

Lifeboats, helicopters and rescue teams working with the French and British navies responded to the incident, which took place as immigration to Britain organised by people-trafficking criminal gangs has become in priority issue for Prime Minister Rishi Sunak's government.

"At 0305 (GMT) today, authorities were alerted to an incident in the Channel concerning a migrant small boat in distress," a government spokesperson said in a statement.

"After a coordinated search and rescue operation led by HM Coastguard, it is with regret that there have been four confirmed deaths as a result of this incident."

An investigation was underway, the spokesperson said.

LBC radio station reported that 43 people had been rescued. A Reuters journalist saw one body bag being removed from a vessel at the lifeboat station in the port of Dover.

The incident occurred just over a year after 27 people died while attempting to cross the sea in an inflatable dinghy in November 2021, in the worst recorded accident of its kind in the Channel.

Temperatures have plunged across Britain in the last week, bringing snow to parts of the country.

Despite the freezing cold, more than 500 migrants have made the perilous journey in small boats since the weekend alone, with the people traffickers who organise the crossings taking advantage of low winds and calm seas.

They have followed the more than 40,000 - a record number - who have arrived from France this year, many having made the journey from Afghanistan or Iran or other countries suffering war and repression to travel across Europe and on to Britain to seek asylum.

In the last year there has also been a significant increase in the number of Albanians crossing the sea. Some British politicians say migrants from Albania - a European Union candidate - have not suffered persecution but are moving for economic reasons.

'Tragic loss'

Ambulances and emergency crews gathered on the quayside at Dover. Sky News said some people had been transferred to a hospital in Ashford, Kent, but it was not known if they were survivors or fatalities.

Speaking in parliament, Sunak expressed sorrow over the tragedy.

"I'm sure the whole House will share my sorrow at the capsizing of a small boat in the Channel in the early hours of this morning and the tragic loss of human life," Sunak said.

"Our hearts go out to all those affected and our tributes to those involved in the extensive rescue operation."

Interior minister Suella Braverman, whose ministry oversees migration policy, put the blame firmly on the trafficking gangs.

"Crossing the channel in unseaworthy vessels is a lethally dangerous endeavour," she told parliament.

"It is for this reason above all that we are working so hard to destroy the business model of the people smugglers: evil, organised criminals who treat human beings as cargo."

Braverman had recently called the wave of arrivals an "invasion", drawing an angry response from Albanian Prime Minister Edi Rama.

The refugee charity Care4Calais accused the government of doing nothing to prevent migrant deaths, which it said were "wholly unnecessary and preventable".

"By failing to act, our government has blood on their hands," the charity said in a statement.

Migrants had suffered horrors such as conflicts, human rights abuses and torture, it said.

"They have been brave and resilient enough to escape and survive incredible journeys to come here and ask for our help. And yet we deny them."

Political pressure

The British government has been under growing pressure to tackle the number of people arriving in small boats after officials and charities condemned the state of migrant centres and the length of time it was taking to process arrivals.

Polls show that the government's inability to halt the arrival of often young men via small boats is also a major frustration for many voters, especially after the country voted to leave the EU so it could better control its borders.

The new incident occurred a day after Sunak announced plans to toughen the laws to stop the boats crossing the Channel, including legislation to prevent migrants from remaining in the country.

Sunak said that Britain's "generosity" was being abused by people arriving illegally. Critics argue that while official routes exist for people to arrive in Britain from Ukraine and Hong Kong, there are no easy ways for people to apply to come to Britain from countries such as Afghanistan and Syria.

Data compiled by the Missing Migrants Project showed 205 migrants had been recorded dead or missing in the English Channel since 2014.