Europol identified 10,700 people suspected of being involved in human trafficking during 2015
Criminal gangs have made human trafficking a money-spinning industry fuelled by a "seismic" development in the trade in Europe, Europol's director Rob Wainwright said.
Europol arrived at the figures through debriefings with 1,500 asylum-seekers, refugees and economic migrants showing that 90pc had paid a criminal gang to reach Europe.
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."
Of a sample of 1,500 migrants, more than 90% claimed to have paid people smuggling gangs
Europol identified 10,700 suspects last year from networks spanning from sub-Saharan Africa to Scandinavia.
It's running in to billions of dollars made by criminal networks in one year alone in Europe
Rob Wainwright, Europol director
Desperate migrants, fleeing in fear and from reported abuse in their homelands, are prepared to pay different gangs of traffickers as different stages to Europe.
To add to their misery some of them are also stripped of their life savings, given seats on boats that are deliberately scuttled or they may face kidnapping or extortion.
The scale of the crisis means that smugglers, many of whom may also be involved in the drug trade, have found a new lucrative supply of victims and governments and law enforcement need to toughen up, according to Mr Wainwright.
He added: "We're going to have to up our game in terms of dismantling this criminal infrastructure in a more successful way than we have done in the past."
Each migrant reportedly pays between $3,000 – $6,000 for help reaching Europe
Some experts predict that numbers of migrants arriving in Europe will be in the millions this year