Laurent Touvet, the prefect of the region, said the three who died were “likely crushed at the bottom of the boat”.

The Abeille Normandie rescued 44 people and allowed 28 people to continue towards UK waters.

Three more are feared dead after being reported missing during a separate crossing attempt.

Mr Touvet claimed the smugglers launched a boat carrying 115 people on Tuesday – one of the biggest ever seen.

The latest Channel horrors came just 12 hours after a woman died when a migrant dinghy “deflated” as it reached UK waters.

The Coastguard issued a Mayday call – which the Daily Express has heard – calling for “any vessels in the area able to assist” to contact the authorities and join rescue efforts.

Witnesses told the Daily Express the French had been following that dinghy for hours before it began to “deflate rapidly” as it crossed into English territorial waters.

But they said French vessels did not rescue migrants from the water. Instead, the migrants were rushed into Dover by Border Force, the RNLI and in a HM Coastguard helicopter.

A source said: “The English vessels were waiting on the border. The French escort vessel was coming up with this dinghy.

“As it crossed the border, it seemed like it started to deflate rapidly. The English vessels rushed in to pick up the people out of the water. The Dover lifeboat was launched and they assisted. But it seemed like the French didn’t pick anyone up.

“It is not a problem for them. In a life-threatening situation [and a Mayday call situation], there’s no worrying about whose territorial water it is.

“The French will always argue that if they get involved and pick them up, they [the migrants] will resist. They don’t want to be picked up by the French because they will be taken back to France.

“This would never have happened if it had not been escorted by the French and if it had been intercepted close to the French shore.”

Shadow Home Secretary Chris Philp said: “Crossing the English Channel in a dinghy is a dangerous and perilous journey that no one should ever take. It is tragic that three more lives have been lost in the Channel overnight.

“The only way to prevent these deaths is to stop the boats leaving in the first place. That means deterrence, removals, and a system that makes clear illegal entry will not work. Labour should never have scrapped the Rwanda deterrent with no replacement. The criminal gangs are running a mock and lives are being lost as a result.

“Britain is paying France hundreds of millions to prevent these crossings, yet it seems the French are doing very little to help. The French must do far more and Labour must face up to the truth – that without a real deterrent, this crisis will never end.

“The French have blood on their hands”.

The female migrant who died on Tuesday was winched from the water, this newspaper understands.

Rescue teams carried out CPR, but she was declared dead after being flown to Dover.

Just 12 hours later emergency crews, including a French navy helicopter, were scrambled to an overcrowded boat off the coast of Pas-de-Calais.

Dozens of migrants attempted an overnight crossing, the authorities believe.

Detailing their rescue operation, the authorities said 44 people were taken off an overcrowded migrant dinghy.

Three people were “unresponsive”, and three more were flown to Boulogne-sur-Mer hospital.

They added: “Twenty-eight of the boat’s occupants refused the offered assistance and continued on their way.”

Migrants sitting in the middle sections of the dinghies are more prone to being crushed, it is understood.

The risk of this terrifying event intensifies if the boat begins to take on water because the vessel essentially collapses in on itself, everyone in the middle amongst the wreckage.

The local prefecture in Calais said: “Three migrants lost their lives, three other people are likely missing.

“The prefect was at the port of Boulogne-sur-Mer this morning, alongside the mayor of Le Portel and the prosecutor of Boulogne-sur-Mer, to oversee the security and rescue operations.

“Smuggler networks bear the responsibility for these tragedies. The State is determined to combat them.”

A UK government spokesperson said: “We are aware of reports of an incident in the Channel in French territorial waters.

“French authorities are leading the response and investigation. We will not be commenting further at this stage.”

At least 20 people are believed to have died while attempting to cross the Channel this year.

The French coastguard claimed 194 people were rescued over September 9 and 10 by state services.

Some 30,838 migrants have crossed the Channel so far this year, up 37% compared to last year.

French union chiefs sparked anger after saying officers would refuse to intercept migrants in the water because it is too cold.

Union barons complained about a lack of training and equipment, adding they were yet to receive any new orders.

The UK has been expecting the French to ramp up interceptions “imminently”.

Similar language has been used for Sir Keir Starmer’s “one-in, one-out” migrant returns deal with Emmanuel Macron.

But neither have yet been operationalised.

Labour’s new Home Secretary, Shabana Mahmood, has vowed to overhaul human rights laws to allow the UK to deport foreign criminals and failed asylum seekers.

But the Attorney General, Lord Hermer, seemingly undermined Ms Mahmood’s pledge, declaring attempts to reform the European Convention on Human Rights was a “political trick”.

The Home Secretary on Monday declared: “The debate in Europe is starting to change. Other countries are actually trying to have this conversation around reform of the convention.

“That’s not been the case previously, where maybe Britain was seen as more of a lone operator, a little bit more isolated in trying to make that case.”

Shadow Justice Secretary Robert Jenrick said: “Labour are bickering amongst themselves while the small boat crisis only gets worse. It’s pathetic. Whatever they say publicly to try and con the public, privately they know their plan to stop the boats won’t work.”

Attorney General Lord Hermer declared ministers are to change the law to stop the European Convention on Human Rights (ECHR) blocking deportations of illegal migrants and foreign criminals.

Lord Hermer, who is a strong supporter of the ECHR, said Labour would “leave no stone unturned” in seeking to toughen up the way the courts applied the ECHR.

He said Strasbourg case law is very “permissive” and allows states an “enormous margin of appreciation” on what they can do in the asylum and immigration space.

“It has developed particularly over the last five or six years, and I am concerned to ensure that domestically, we have kept pace with that.

“Some of our colleagues on the Council of Europe have, I think, more effective, more robust mechanisms that are compliant with Article 8 that we need to look at. We are kicking the tyres hard at every level.”

He said this included looking at case worker guidance, immigration rules, primary legislation, and the Government adopting a “very proactive litigation strategy”.

The Attorney General said France and Germany, as well as other European nations, would ditch migrant returns deals with the UK if it left the ECHR.

“It’s inconceivable our partners would have entered into these agreements if we were not members of the Council of Europe,” Lord Hermer said.