There are slaves in Britain today. Impossible, most people would say. Not so. It is just that they are hidden away. It is a problem which both the police and the Home Office acknowledge, but which is kept out of the political spotlight because of contradictions between the Government's attitude to immigration - on which it seeks to placate populist opinion - and its avowed determination to crackdown on people trafficking.
What do we mean by slaves? Anyone who is forced to work through coercion or deception, for little or no pay, and who is controlled by an "employer", usually through mental or physical abuse or threats. The International Labour Organisation estimates that there are at least 360,000 people living in slavery in industrialised countries. Two-thirds have been coerced into forced labour by people traffickers in a worldwide industry worth at least $32bn a year. This is plainly big business.
No one knows how many of these people are in the UK. There are thought to be thousands of people in Britain who are slaves today. Most of them are caught in deliberately sprung debt traps. They have been tricked into taking a loan for as little as the cost of medicine for a sick child - or more commonly to buy passage into the UK.
To repay the debt, many are forced to work long hours, seven days a week, up to 365 days a year. They receive basic food and shelter as "payment" for their work, but may never pay off the loan. Such unfortunate people are to be found in agriculture, construction, cleaning and domestic work, food processing and packaging, care and nursing and the restaurant trade.
British politicians are happy to fulminate about the iniquities of people trafficking. But they have created a legal and political framework which makes it virtually impossible to take sustained and effective action against the criminal gangs who undertake the trade.
After the incident in which 23 Chinese cockle-pickers in the thrall of a gangmaster lost their lives in Morecambe Bay, the Government made trafficking for forced labour a criminal offence. A licensing system came into force this year. And the Government is setting up a UK Human Trafficking Centre with a mandate to pursue trafficking for both labour as well as sexual exploitation.
Yet despite these positive initiatives, there has not been a single successful prosecution for the offence since it was introduced in 2004. Nor is there any special assistance available to people who are trafficked for forced labour. Most mystifyingly, the Government still has not signed the Council of Europe Convention on Action Against Trafficking in Human Beings, which would ensure that people trafficked into forced labour are provided with minimum standards of protection and support. More than 30 other European countries have signed.
Why this lamentable failure? A central reason is that the investigation of trafficking is fatally hampered by the UK immigration policy and the "prism" of organised immigration crime, through which trafficking is seen at the policy level.
For the police to have any prospect of catching those who run international networks, they must have the co-operation of the victims. However, when the victims have irregular status in the country, there is limited incentive for them to co-operate with the police. The police cannot guarantee them protection, access to services or an opportunity to regularise their status. They can only try to negotiate protection for them with the Immigration Service, which often attempts to deport victims whom the police would regard as witnesses and expect to be treated as victims of crime.
This is because the Immigration Service works on a quota system of deportations. So for immigration officials, there is limited incentive to stop the deportation of victims of trafficking, even if it assists police enquiries. This situation is likely to get worse, not better.
Under the Government's latest proposals, the number of deportations will increase from next month. This will further hamper the pursuit of criminals, for the victims of trafficking are even less likely to co-operate with the police if they are immediately to be deported back to the very countries where those criminal gangs still hold sway.
The result is a system whose priorities are upside down. Instead of protecting the rights of victims, the system punishes them. Trafficked people can be detained, charged or prosecuted for immigration offences such as illegal entry or destroying their documents, although this is most likely to have happened as a result of coercion from the traffickers.
What all this means is that trafficking people to the UK remains a high-profit, low-risk business for those criminal gangs who organise it. In countries like Germany and Italy, which have signed the European Convention Against Trafficking - and where minimum standards of protection to the victims of human trafficking now exist - prosecutions have increased. In the UK there has still not been not been a single prosecution.
This situation has always been unacceptable from a human-rights perspective. What is clear now is that it is unjustifiable from a law-enforcement perspective as well.
The writer is director of Anti-Slavery International, one of the charities supported by the 'Independent' Christmas appeal