Harrowing sounds of calls from desperate migrants were recorded as they asked for help before their boat capsized in the English Channel, leaving four dead.
The Royal Navy, French navy, Coastguard and RNLI lifeboats were all involved in a major rescue operation off the Kent coast on Wednesday morning.
RNLI lifeboats were launched from Dover at 3.07am, followed by more from Ramsgate and Hastings.
A harrowing 22-second WhatsApp note was left by one man on board who pleaded for assistance as water entered their boat.
He could be heard shouting: "We have children and families in a boat. Water is coming in. We don't have anything for this."
Nikolai Posner, communications officer for Utopia 56, a charity helping migrants in the channel, said charity workers attempted to respond, but their message was not received.
In the message, a man can be heard saying there was water inside the boat with "families and kids" on board, Mr Posner told PA.
He said: "It was clearly an emergency, he was calling for help ... In the background of the message we can hear babies screaming."
Mr Posner said the charity tried to respond to the message but the reply was not received, then they contacted both the French and UK coastguards.
In audio of the voice note, obtained by Channel 4 News, the man can be heard saying: "We're in a boat and we have a problem.
"Please help. We have children and families in a boat. Water is coming in. We don't have anything for this, for feeling safety. Please help me bro. Please, please. We are in the water. We have a family."
It is unclear why a rescue boat was only launched an hour after the charity informed authorities of the distress message, Mr Posner said, adding: "We don't know what really happened during that time."
A Government spokesman said: "At 0305 today, authorities were alerted to an incident in the Channel concerning a migrant small boat in distress.
"After a co-ordinated 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. Investigations are ongoing and we will provide further information in due course.
"This is a truly tragic incident. Our thoughts are with the friends and families of all those who have lost their lives today."
Government sources told the PA news agency 43 people were rescued, with more than 30 of those pulled from the water.
Meanwhile, a fisherman told Sky News that migrants surrounded his boat in the early hours of the morning "screaming for help".
The skipper, named only as Raymond, said his crew saved 31 people stranded in the Channel, adding: "It was like something out of a Second World War movie - there were people in the water everywhere, screaming."
Footage broadcast by Sky News showed a group of people, squashed inside a sinking dinghy which was filling with water, being hauled up over the side of a boat with rope.
In the Commons, Mr Sunak said: "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.
"Our hearts go out to all those affected and our tributes to those involved in the extensive rescue operation."
Labour leader Sir Keir Starmer said: "Our prayers go out to those who capsized in the freezing waters of the Channel last night. It's a reminder that the criminal gangs running those routes put the lives of the desperate at risk and profit from their misery. They must be broken up and brought to justice."
Dover and Deal MP Natalie Elphicke urged Mr Sunak to "meet urgently" with French President Emmanuel Macron to set up joint patrols in the Channel and on the beaches to prevent boats entering the water and to save lives.
"Urgent action is needed now," the Tory said.
Four people have died after a migrant boat capsized in the English Channel.
Prime Minister Rishi Sunak expressed his "sorrow" at the "capsizing of a small boat" in the Channel, telling MPs there had been a "tragic loss of human life".
