A former Bradford police chief, in charge of rescuing victims of human trafficking, has welcomed a Government proposal to introduce a maximum sentence of life imprisonment for the offence.

The draft Modern Day Slavery Bill sets out the Government's plans to tackle the problem of people being trafficked into the UK to work in conditions of slavery, pulling together into a single act the offences used to prosecute slave-drivers.

Home Secretary Theresa May said it was impossible to know how many people are being held in conditions of servitude in Britain, but referrals to official agencies suggest the numbers are growing.

It is hoped the changes in the Bill will increase the number of prosecutions from the single figures seen in recent years. Mrs May said one of the obstacles to successful prosecution was the reluctance of victims to come forward because of fears they might themselves face prosecution or be sent back to their home countries.

New guidance is being drawn up by the Director of Public Prosecutions to protect victims of slavery from being prosecuted for crimes which they have been forced to commit because of their illegal servitude, she revealed.

The Bill contains provisions to give automatic life sentences to offenders who already have convictions for very serious sexual or violent offences. It introduces Trafficking Prevention Orders to restrict the activity and movement of convicted traffickers and stop them from committing further offences. And a new Anti-Slavery Commissioner will be appointed to hold law enforcement and other organisations to account.

Former Chief Superintendent Allan Doherty, the Bradford-based director of operations for the charity Hope For Justice, said: “We are happy about the Bill. We have been involved in consultation and will continue to be. We want to keep the topic of trafficking high on the agenda so people can understand it and report it if they see signs of it, and so police nationally can understand it is a massive issue to take seriously and put resources into it.

“At the moment the police are being pulled in a lot of directions. We are happy human trafficking is becoming a priority and probably a lot more resources will be devoted to human trafficking.”

Hope For Justice has rescued nearly 150 victims in the UK in two years. The Bradford team alone rescued 20 people in just two weeks.

Mr Doherty said: “The Bill acknowledges that modern day slavery is being recognised at the very highest level. That is very helpful because it sends a strong message, to police forces, local authorities and other people who will come across victims, to take them seriously.”

West Yorkshire Police and Crime Commissioner Mark Burns-Williamson called for the Bill to go further to provide stronger legal protection for child victims.

He said: "I have pledged to work with fellow Police and Crime Commissioners and internationally to tackle issues such as trafficking and forced marriage and plan to meet with more charities who work with victims of this awful practice to learn more about what we can do to help.

"I will be looking at the scale of this problem in West Yorkshire and how it can be measured accurately so we can develop ways of tackling it to ensure we are making communities safer and feeling safer."