The former prime minister says criminal gangs could exploit the changes he wants to introduce.
Sadia Ali, co-founder of Minority Matters, discusses how criminal gangs use children to move drugs across the country, along "county lines" and how the effects are being felt in already marginalised minority groups the most.
Home Office immigration rules also put vulnerable people at risk of modern slavery, warns Crisis.
More than 10,000 people were identified as potential victims of forced labour last year. But a lack of frontline services this year has seen figures drop.
The 20-year-old woman from Romania was told she'd be working in a factory in the UK by the brothers, who then hid her passport and violently abused her.
Gwent Police are investigating allegations that some care home staff are victims of modern slavery.
Gangs are using soup kitchens, drop in centres and homeless shelters as recruitment grounds for slave labour.
Maria Miller forced a 74-year-old woman to sleep in an outhouse and to go for days without food.
Police were called just before 7.10am on Friday to Newlyn in Cornwall.
It is estimated that 13,000 people are held in a situation of modern slavery in the UK and this could be the tip of an iceberg. For those that do escape, a unique course at Northern College in Barnsley is helping survivors to become more resilient and rebuild their lives.