An anti-slavery coalition is calling on the government to add strong measures to the draft Modern Slavery Bill so it is effective and reduces trafficking and slavery.

The Evangelical Alliance and 14 other organisations make up the coalition, including A21 Campaign, CARE, The Salvation Army, Hope for Justice, Love 146, International Justice Mission and Stop the Traffik.

The coalition briefing calls for an end to modern slavery once and for all: "The transatlantic slave trade was banned in 1807 and slavery was abolished across the British Empire in 1834, yet it is still with us today. Children are sold into slavery to pay family debts; people pay for passage, only to be trafficked over borders and find forced labour conditions rather than freedom ... this must end."

Dr Dave Landrum, director of advocacy at the Evangelical Alliance, said: "For evangelicals this is unfinished business. We've been fighting slavery for hundreds of years, and we are still at it today. This bill needs to live up to its promise. It has the potential to tackle modern slavery but needs to listen to the campaign groups in order to achieve that aim. Together as organisations motivated by our Christian faith we call on the government to act and strengthen the bill so it can bring freedom to many caught in slavery."

The call comes today, as the government issues their draft of the Modern Slavery Bill and Frank Field MP publishes his evidence review. Following the publication of the Centre for Social Justice's report It Happens Here in March 2013, pressure has built for the government to introduce a new law. The proposals increase the maximum sentences and bring together offences currently dealt with under different strands of the legal system.

Churches are urged to meet with their MPs and encourage them to take a strong and uncompromising stance against all shades and forms of modern-day slavery when the bill comes up for debate at Westminster in 2014

Specifically, the coalition wants the government to act in three ways: to put a special focus on victims, ensuring they are properly identified, able to receive immediate assistance and that the circumstances of their victimisation are fully investigated; to ensure the anti-slavery commissioner is accountable to parliament and able to speak across all parties, give a voice to victims, and have the power to launch inquiries, publish findings and hold the culpable to account. Third, it is calling for the law to insist on greater transparency by requiring businesses to make public their information on measures taken to eradicate modern slavery from their supply chains and business practices.

The evidence review conducted by Frank Field – and published simultaneously to the draft bill – identified similar areas for improvement in the draft bill and the anti-slavery groups hope the government will refine the bill to incorporate these aspects.

Nola Leach, chief executive of CARE, commented: "The government must seize this opportunity to set a new standard in the care and protection of survivors. A bill without victims at its heart will be only a half measure. Together, we must act to support the vulnerable and expose those who exploit them."

Terry Tennens, executive director of International Justice Mission UK, said: "From extensive international experience, IJM has learned that holding institutions designed for security and protection accountable is a highly effective way of protecting the vulnerable from violence and exploitation."