At least 31 people – including a small child – have died while crossing the Channel from France to England in a catastrophe leaders have called the result of “murder” by people smugglers.

Three times as many migrants have attempted to make the dangerous journey through the Dover Straight in small dinghies this year compared to 2020.

On Wednesday (local time), more boats than usual left France’s northern shores to take advantage of calmer conditions in the busy shipping lane.

But while the waves were smaller, they still had power to upturn small boats – and the water was bitterly cold.

One fisherman called authorities after seeing an empty dinghy and people floating – either unconscious or already dead – face-down in the water.

Rescue teams rushed to the scene and recovered 31 bodies.

Dozens of men, five women and a little girl are among the confirmed victims. Two people were still missing as of early Thursday morning (Australian time).

Jean-Marc Puissesseau, president of the ports of Calais and Boulogne, said he was in shock.

“They are murderers, they are really murderers. And of course we are all so upset,” he told the BBC. 

“You know we are used to the migrants and we know that it cannot continue. We knew that there would be a catastrophe and we had that today.”

The disaster is set to put pressure on French and British leaders to reassess their approach to people smugglers.

France’s President Emmanuel Macron said “France will not let the Channel become a cemetery” as he promised that authorities would track down the criminals who sold men, women and children a spot on the dinghy.

UK Prime Minister Boris Johnson admits efforts to stem the flow of migrants crossing the Channel in small boats “haven’t been enough”.

“What this shows is that the gangs who are sending people to sea in these dangerous crafts will literally stop at nothing,” Mr Johnson said.

“Our offer is to increase our support but also to work together with our partners on the beaches concerned, on the launching grounds for these boats.

“That’s something I hope will be acceptable now in view of what has happened.”

Mr Johnson said the “gangs” organising the dangerous journeys needed to be shown “their business model won’t work, that they can’t simply get people over the Channel from France to the UK”.

Otherwise, he said, “they will continue to deceive people, to put people’s lives at risk and, as I say, to get away with murder.”

French police have been patrolling the beaches near Calais where it’s common for them to find deflated dinghies. Photo: AAP

The BBC reports at least 10 migrants have died while trying to make the crossing in recent weeks.

The UK has promised to give France £54 million ($100 million) this financial year – but Mr Johnson said it was now clear that had not been enough.

The BBC reports Mr Johnson’s critics have accused the government of failing to deliver on pledges to reduce the crossings and said more law enforcement work was required – as well as more work creating safe and legal routes for migrants.

Early Thursday morning, the search was continuing for survivors.

Three helicopters and police and rescue boats were still at the scene. Police were also checking beaches in the French town of Wimereux, in the hope survivors may have made it to shore.

One fisherman, Nicolas Margolle, told Reuters he had seen two small dinghies earlier on Wednesday, one with people on board and another empty.

Early on Wednesday, Reuters reporters saw a group of more than 40 migrants head towards the UK on a dinghy.

The BBC reported that more than 25,700 people have made the dangerous journey to the UK in small boats this year – more than three times the 2020 total.

About 25 boats had attempted the crossing so far on Wednesday, according to BBC reporters.