Investigation finds sunken migrant boat was "wholly unsuitable and ill-equipped for the crossing attempt".
The Maritime Rescue Co-ordination Centre at Dover was informed that an inflatable boat carrying migrants was potentially in distress at 2.13am on December 14, 2022.
An investigation into the sinking of a migrant boat in the Channel, which claimed at least eight lives in December 2022, has found the dinghy was "wholly unsuitable and ill-equipped for the crossing attempt".
The report by the Marine Accident Investigation Branch (MAIB) also revealed the occupants could only raise the alarm by mobile phone.
The Maritime Rescue Co-ordination Centre at Dover was informed at 2.13am on December 14, 2022 that an inflatable boat carrying migrants from France to the UK was potentially in distress.
At around 3am, the vessel suffered "structural failure and many of the migrants entered the water", the MAIB said.
Thirty-nine were rescued, but at least eight died, with four bodies recovered to the UK and the others lost at sea.
All of the occupants of the boat were male and aged between 13 and 35.
Their nationalities were a mixture of Afghan, Sudanese, Indian, Uzbek and Albanian.
The MAIB concluded: "The inflatable boat was wholly unsuitable and ill-equipped for the crossing attempt and the occupants' only method of raising the alarm was via mobile phone."
The report said that at 1.53am, a volunteer for French charity Utopia 56 received a global positioning system location in the Channel and a WhatsApp voice message that said: "Hello brother, we are in a boat and we have a problem, please help.
We have children and family in a boat and water come in the boat and we do not have anything for the children safety. "
"Please help bro. Please, please, please, we are in the water. We have a family."
The sound of someone "crying loudly" could be heard in the background, the MAIB said.
The volunteer unsuccessfully attempted to contact the sender, before alerting authorities in Dover and Calais.
Investigators believe this was a "false declaration intended to expedite rescue" but at around 3am the occupants of the dinghy heard "a pop or bang and the boat started to flood rapidly from under the floorboards", the report stated.
Several of the migrants entered the water, while some were able to stay on the tubing.
The report said it was "fortunate" the boat failed "in very close proximity" to fishing vessel Arcturus, whose crew recovered 31 occupants.