A small boat carrying about 40 migrants has sunk off the south-eastern coast of England in freezing temperatures, killing some of those on board, the BBC reports.

Britain’s government and emergency officials confirmed the incident was ongoing, with lifeboats, helicopters and rescue teams working with the French and British navies to respond to an event that occurred at 3.40am on Wednesday.

British radio station LBC reported 43 people had been rescued, with “a small number” having died.

“We are aware of an incident in UK waters and all relevant agencies are supporting a co-ordinated response,” a spokesperson for the government said.

“Further details will be provided in due course.”

Temperatures plummet across Britain

Temperatures have plunged across Britain in the past week, bringing snow to parts of the country. The temperature was two degrees in a nearby town on Wednesday morning.

Ambulances and emergency crews gathered on the quayside at the port of Dover to handle Wednesday’s sinking.

Sky TV said some people had been transferred to a hospital in Ashford, Kent, but it was not known if they were survivors or fatalities.

“I am aware of a distressing incident in the Channel this morning and I am being kept constantly updated while agencies respond and urgently establish the full facts,” Britain’s interior minister Suella Braverman said on Twitter.

“My heartfelt thoughts are with all those involved.”

PM signals tough stance on Channel crossings

The latest incident came a day after Prime Minister Rishi Sunak announced plans to toughen laws to stop small boats crossing the Channel, including legislation to prevent migrants from remaining in Britain.

Mr Sunak said the government was sending a message that “enough is enough” and people were “right to feel angry” about repeated failures to tackle the issue.

Polls have shown that the government’s inability to halt the arrival of often young men via small boats is a major frustration for many voters, especially after Britain voted to leave the European Union so it could better control its own borders.

The government has said that a tougher line was also needed to deter people from risking their lives, and breaking the business model of people traffickers who arrange the journeys at great cost.

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

In the worst accident of its kind, 27 people died while attempting to cross the Channel in an inflatable dinghy in November 2021.

-AAP