Update 4th September 2020: French authorities have since said that they believe the victim was 28 years old.
A 16-year-old from Sudan who disappeared at sea has been found dead on a French beach.
French politicians believe the boy, whose body was found in Calais, went missing while attempting to cross the English Channel in a small boat.
A search operation began after another migrant was found with hypothermia on the shore at about 02:00 BST.
He told authorities that his friend, who could not swim, was missing after their makeshift boat capsized.
UK Home Secretary Priti Patel said the death of the young migrant was a "brutal reminder" that people smugglers exploit the vulnerable.
Bridget Chapman, of Kent Refugee Action Network, said that the government was wrong to focus only on the criminals organising crossings, adding that reports the boy had pushed off in a makeshift boat made it "likely that people smugglers weren't even involved".
She called on the Home Secretary to instead "turn her attention immediately to creating safe and legal routes so that no on else suffers the same fate".
Labour MP Nick Thomas-Symonds, the shadow home secretary, said the government's response to the rise in crossings had been "lacking in compassion and competence".
He urged ministers to "step up work with international partners to find a humanitarian solution to this crisis, which is costing lives".
The Home Office would not confirm whether the boy had been trying to reach the UK.
Asked to clarify if there was evidence people smugglers were involved in the death, it said it would not comment on an investigation that is being lead by the prosecutors' office in Boulogne-sur-Mer.
A further 41 people on four boats were rescued by French authorities after getting into difficulty on Wednesday. One had fallen overboard and was pulled from sea at about 07:30.
More than 4,800 people have reached the UK after crossing the Channel in about 360 small boats this year.
Labour leader Sir Keir Starmer said: "The death of a 16-year-old child in the Channel is a tragedy. My thoughts are with his loved ones.
"This is a humanitarian crisis that needs a compassionate response."
The Bishop of Dover, Rev Rose Hudson-Wilkin, said: "People who try to cross the Channel seeking safety and security are not criminals - they are human beings, like you and I.
"Human beings who should be afforded the dignity and respect and rights that so many of us take for granted.
"It is a travesty that this young man will never see his hoped-for future, that his family has been deprived of seeing him grow up."
'Don't deserve to die'
Clare Moseley, of refugee charity Care4Calais, said she was "absolutely devastated by the unnecessary death of this child".
"We can only imagine the fear he felt and our hearts go out to his family," she said.
Ms Moseley said the boys the charity supports in Calais were "fun to be with despite the horrors they have been through".
"Some are cheeky, some are smart, some like football, some like books. None deserve to be here and none deserve to die alone in the sea."
Mike Adamson, chief executive of the British Red Cross, said: "It should not be the case that people feel they have no choice but to make such dangerous journeys in their search for protection.
"At a time when more than 1% of the world's population has been displaced, we need countries to work together to provide the best humanitarian outcome."
French minister Marlene Schiappa said the boy's body was found on a beach in Sangatte, Calais, on Wednesday.
Calais MP Pierre-Henri Dumont said it "seems pretty sure he drowned in the Channel".
Earlier this month, Dan O'Mahoney was appointed as the UK's Clandestine Channel Threat Commander in a bid to make the Channel route "unviable" for small boat crossings.
But Mr Dumont said "whatever the British government implement in the Channel, people will try to cross".
"The more difficult it will be to cross, the more dangerous it will be," he added.
He said the "only solution" was to allow migrants living in Europe to claim asylum in the UK, without having to land in Britain.
Immigration minister Chris Philp said the "awful tragedy near Calais shows how dangerous this migration route is".
"We will redouble our work to agree and implement a new plan with France with the aim of completely stopping these boat crossings, which are facilitated by ruthless criminals and which risk lives."