Dear John 

Statistics on modern slavery in the UK

We recently completed our compliance check of your Modern slavery in the UK and Child victims of modern slavery in the UK compendium articles against the Code of Practice for Statistics. We carried out a complementary compliance check of Home Office’s National Referral Mechanism (NRM) statistics, as the articles identify the NRM statistics as the best available source of the number of potential modern slavery victims in the UK.  

Modern slavery is a term for all forms of human trafficking, slavery, servitude and forced labour. Measuring the prevalence of modern slavery is challenging because there is no single source or method that can accurately quantify the number of victims. Our review focused primarily on the value and coherence of the articles, looking at how they bring together and explain statistics and data from a range of sources.  

Both articles are standalone releases, and there are currently no plans to update them. Given the importance and public profile of modern slavery, and the insight generated by the articles, we encourage you to put in place plans to update them, particularly the modern slavery in the UK article. We identified a number of strengths as well as a couple of ways in which the value and quality of the articles could be enhanced.  

Both articles draw on a wide range of data sources to present a detailed picture of the scale and nature of modern slavery. They bring together official statistics from UK Government departments and the Devolved Administrations, with data which are not official statistics, from the Crown Prosecution Service, charities and support services. The statistical commentary is clear and accessible, with explanations of key trends in the data and reasons for changes over time. The modern slavery in the UK article contains a wealth of background information and context, including an excellent flow chart of the NRM process, through which potential victims are referred.   

We found a range of other positive features that demonstrate the value and quality of the statistics: 

  • The collaborative approach used to produce the articles is excellent. Your team worked with stakeholders across academia, government and the third sector to understand information needs, source data, and review data quality. The guest blog post by Professor Sir Bernard Silverman, published on the same day as the modern slavery in the UK article, is a good endorsement of the collaboration and the value of the articles. 
  • The articles are some of the few statistics outputs that bring together crime and justice data from England and Wales, Scotland and Northern Ireland. The driver for creating a UK view is the UN’s Sustainable Development Goals (SDG) indicators, several of which measure the UK’s progress towards combatting modern slavery. For some sources, data from UK countries cannot be combined due to differences in definitions and recording processes – for example, for modern slavery offences recorded by the police. Nonetheless, the articles provide the most comprehensive and coherent picture of modern slavery in the UK.  
  • The articles demonstrate a good awareness of the sensitive nature of modern slavery. Both articles contain a ‘Finding help’ section, with contact details of victim support services. The child victims article intersperses statistical commentary with quotes from victims. This is a powerful way of bringing the statistics to life and highlighting the impact of modern slavery on victims.   
  • Both articles are clear about the challenges of measuring modern slavery; in particular, the lack of a definitive source of data or suitable method to quantify the number of modern slavery victims in the UK. The articles are transparent about the nature of all data sources and their limitations, including the lack of comparability of data sources due to differences in coverage or data collection methods.  
  • The framework used to evaluate and categorise relevant data sources – each data source has been badged as a ‘legal’, ‘support’ or ‘awareness’ indicator – is sensible and helps users understand the complexity of the modern slavery data landscape. It is good that this framework was developed and tested with stakeholders.  
  • The accompanying article on Sourcing data on child victims of modern slavery gives a clear overview of how suitable data sources were identified and reviewed for the SDG indicators relating to modern slavery and children in the UK. 

We also identified two ways in which the quality and value of the statistics could be enhanced: 

  • To aid user understanding of the quality of all data sources, information should be added on the strengths and limitations of data which are not official statistics, including data from victim support services, helplines, and applications, and how data from these sources were reviewed and quality assured. We encourage the team to continue exploring other data and data sources that could add insight on modern slavery. 
  • Signposting between the two articles could be improved, particularly as the child victims’ article does not contain the same level of detail as the modern slavery in the UK article. We recognise that the child victims’ article was reduced in size to make it more accessible and user-friendly.   

Thank you to your team for its positive engagement during this review. We look forward to continuing to engage with your team. Please get in touch if you would like to discuss any aspects of this letter further or if we can offer further assistance as these statistics continue to develop. 

I am copying this letter to Meghan Elkin and Peter Jones, heads of the Centre for Crime and Justice at ONS; Tom Bucke, Head of Unit for Drugs, Exploitation and Abuse Analysis at Home Office; and Jon Simmons, Head of Profession for Statistics at Home Office. 

Yours sincerely 

Mark Pont 

Assessment Programme Lead 


Related Links:

Mark Pont to Jon Simmons: National Referral Mechanism and Duty to Notify statistics