Criminal gangs organising the trafficking of illegal migrants across Europe’s porous borders have made an estimated profit of almost £4 billion in the past 12 months alone, according to the European Union’s law enforcement agency Europol.

Europol’s director Rob Wainwright told the Independent on Sunday that the figures were established through debriefings with 1,500 migrants which showed that 90 per cent had paid a criminal gang to reach Europe via a Mediterranean crossing.

Mr Wainwright said: “We also know that, on average, each migrant is paying between 3,000 and 6,000 dollars to a criminal facilitator for their journey.

“So you do the simple math and you’re up to a turnover in 2015 of between three and six billion dollars. They are big figures. It’s running in to billions of dollars made by criminal networks in one year alone in Europe.

“Last year has been seismic in the development of the people-smuggling trade in Europe in particular, and we are now talking about its being a multibillion-dollar industry in the way it hasn’t before, and the Champion’s League of criminal sectors in Europe alongside drugs.”

Europol identified 10,700 suspects last year from networks spanning from sub-Saharan Africa to Scandinavia. They have helped create the migration invasion that saw one million people land on European soil in the past 12 months alone, for the most part drawn by German Chancellor Angela Merkel’s ‘open door’ offer to anyone who arrived on the country’s doorstep.

With many of the people-smuggling networks now expanding into other criminal enterprises such as narcotics trafficking, security services and governments need to redouble their efforts to shut them down, Mr Wainwright told the newspaper.

“Criminals that were active in the drugs business or predominantly active in the people-smuggling business are now turning their hand to a bit of both and are finding that their contacts and networks and routes and methods of concealment can work in both fields.”

The cost of the invasion is not just being borne by those trying to enter Europe. As Breitbart London has reported, the ease of passage afforded illegal migrants may be diminished if Germany ‘s proposal for a pan-European tax on petrol and diesel is backed to pay for the Continent’s border security.

Speaking in an interview with Süddeutsche Zeitung, Wolfgang Schäuble said securing the external borders of the Schengen free movement zone was a top priority, and attempts to protect it “must not fail due to a limitation of funds”.

“Why shouldn’t we deal with this at a European level, if the task is so urgent?” he added. “We need to secure the Schengen external borders now.”

Securing those borders will cost money and the only way to set up a new revenue stream in Mr Schäuble’s estimation is more taxes.

Mr Wainwright agrees on the need for better borders, but he wants to see money sent to Greece so it is supplied with the technology, manpower and resources to carry out effective security screening of all new arrivals.

“When you put the external border of the EU under such strain that it has to cope with a million new arrivals at just a few of the external border points, then you can see how difficult it is to run a systematic and reliable screening process,” he said. “This is the single most important thing to get right: to make sure that we can help the Greek authorities, who have been swamped.”