Investigators say more asylum seekers may have drowned when a migrant boat sank in the Channel.

The Marine Accident Investigation Branch (MAIB) is now carrying out a full investigation into the circumstances of the tragedy, which claimed the lives of at least four people when the vessel capsized.

According to the maritime watchdog, "the exact number of persons in the boat has not yet been established" following the incident on December 14.

In all, 39 people were rescued from the ice-cold Channel waters in a joint search and rescue mission led by the Coastguard.

A spokesman for the MAIB said: "The MAIB has launched an investigation into the sinking of a migrant boat in UK waters while it was attempting to cross the English Channel on December 14, resulting in four confirmed fatalities.

"The focus of the investigation will be on the UK's emergency response. The mechanism for the foundering of the small boat will also be explored."

A teenager was later charged by Kent Police for piloting the doomed vessel.

Ibrahima Bah appeared at Folkestone Magistrates' Court on December 19 and pleaded not guilty to facilitating attempted illegal entry to the UK.

Following the tragedy, charities described the deaths "wholly unnecessary and preventable" and called for safe passage for asylum seekers.

A record 45,756 asylum seekers crossed the Channel to the UK in small boats in 2022, according to government figures.

The Home Office resumed responsibility for Channel crossings in January following eight months of the Royal Navy taking charge of operations.

A "worst-case scenario" of 80,000 crossings taking place this year has been made by the Home Office, nearly double the record number in 2022.

The government is already planning to recruit another 100 officers to deal with the number of people trying to make it to the UK on small boats.