A government study into the scale of modern slavery in Britain suggests that up to 13,000 people in the country are victims — four times the previous estimate.

The Home Office figures released Saturday aimed to calculate the number of previously unreported victims. They include women forced into prostitution or sexually exploited for profit, domestic workers, and laborers on farms, factories and fishing boats.

The agency says many of the victims are brought in by traffickers from countries including Romania, Poland, Albania and Nigeria.

The report is part of the British government's strategy to tackle trafficking and other forms of modern slavery. Legislation on the topic is being debated in Parliament.