Dozens of arrests have been made in the biggest international police operation of its kind to catch a people smuggling gang suspected of being behind thousands of Channel crossings.

A slew of raids took place in the UK, Germany, France and the Netherlands on Tuesday as part of a joint operation co-ordinated by Europol with Eurojust, the European Union’s criminal justice co-operation agency.

Operation Punjum, led by the National Crime Agency (NCA) in the UK, was carried out alongside Operation Thoren in Europe to target an organised crime gang suspected of smuggling up to 10,000 migrants across the Channel in the last 12 to 18 months.

It is understood there have been in excess of 40 arrests across all the countries involved, with several hundred life jackets found and 50 small boats, such as dinghies, recovered at one location alone.

In London, NCA officers arrested a 26-year-old man in Rushey Green, Catford, and a 22-year-old man in St Davids Square, on the Isle of Dogs, on suspicion of conspiring to facilitate illegal immigration.

The NCA’s director of threat leadership, Chris Farrimond, said these arrests were believed to be “directly linked to the operation”. The men remain in custody and are being questioned by NCA investigators.

Of four other arrests made, two were “believed to be illegal migrants” and have been handed over to immigration authorities, while two others were detained on drug offences.

The NCA described the raids as the “biggest ever international operation targeting criminal networks suspected of using small boats to smuggle thousands of people into the UK”.

Prosecutors in the north-western city of Osnabruck were reportedly in charge of the German raids.

Some 900 officers from the federal police and the Osnabruck police headquarters were involved in 36 searches of properties, with 18 people arrested in Lower Saxony, Bremen, North Rhine-Westphalia and Baden-Wurttemberg, Germany’s press agency dpa said.

The NCA said all of the countries had been working together as part of a long-running taskforce to tackle people smuggling and Channel crossings and investigations began with the arrest of a suspected people-smuggling “kingpin” in London earlier this year.

Mr Farrimond told reporters at a briefing: “It was actually our intelligence which started this all off and which led to the culmination (on Tuesday).

“Many of those arrested overseas have been targeted as a result of evidence that we provided into the taskforce.”

Iranian Hewa Rahimpur, 29, who was living in Ilford, east London, was arrested in May suspected of being a leading figure in a network organising human trafficking via small boats and is facing extradition proceedings to send him to Belgium.

Asked how much the gang was believed to be charging migrants to cross the Channel after lining up boats, engines and life jackets for them, Mr Farrimond said a “straight trip across the Channel” was estimated to be charged at between 2,500 and 3,500euros.

But he added that most people ask for help to travel across Europe as well which would cost more.

More than 12,800 migrants have arrived in the UK so far this year after navigating busy shipping lanes from France in dinghies and other small boats, according to provisional Government figures. Official records show 28,526 crossed last year.

While this operation alone “will not stop the flow of migrants to the UK”, Mr Farrimond said he believes the scale of the work will “absolutely” make a dent, adding: “It will take some time for this group, or whichever group succeeds it, to recover. Now we’re not going to stop at this point.

“Ideally we’d like to stop the supply of small boats much earlier on so that they really have difficulty getting their hands on them.

“And we’d also like to attack the money flows in a lot more detail than we do right now. So there’s plenty more to do. It’s not going to stop it but it is going to make a dent.”

Home Secretary Priti Patel said the latest operation shows Britain will “stop at nothing” to end the illegal people-smuggling trade.

She said: “These arrests send a clear message to the criminal gangs who are preying on vulnerable people across Europe and beyond: we will stop at nothing to end your sordid trade, bring you to justice and save lives.

“This hugely significant operation once again shows the NCA and our international partners working diligently to dismantle people-smuggling networks.

“These callous individuals treat human lives as a commodity and we will continue to work with our partners to ensure that they feel the full force of our new, tougher laws designed to break their business model and suitably punish them for their despicable crimes.”

More information on the European operation is expected to be provided at a Eurojust press conference in The Hague in the Netherlands on Wednesday.