Around 140,000 people are being held in conditions of effective slavery in Europe after being smuggled by human traffickers, according to a United Nations organisation.
The UN Office on Drugs and Crime has launched a one million US dollar fund in London which will offer small grants to charities and other groups providing help to the victims of trafficking.
Executive director Yury Fedotov acknowledged that the fund could cover only a fraction of victims' needs, and appealed to governments and businesses to make further donations.
Mr Fedotov told the BBC Radio 4 Today programme: "At any given time, approximately 2.5 million women, children and men are trafficked. It is a huge criminal business worth around £32 billion. In Europe alone, the estimated value of trafficking is about £3 billion.
"The victims are mostly women and children, but also men. It is a crime that needs to be addressed in an appropriate and more co-ordinated way.
"We need to help victims of human trafficking in any way we can."
Mr Fedotov said organisations supporting trafficking victims have until May 1 to make applications for small grants, which are intended to fund safe havens, legal representation and material support for those who escape their captors.
The cross-border nature of human trafficking makes it "one of the most difficult crimes to address", said Mr Fedotov, adding: "It is very hard to prosecute people without very strong and active international co-operation.
"So far, I wouldn't say we have had tremendous success. For every 200,000 victims of human trafficking, there have been only three cases of people arrested and prosecuted."
