Modern Slavery Act compliance for UK Main Contractors

The Modern Slavery Act 2015 is a key piece of UK legislation designed to tackle illegal labour practices such as slavery, servitude, forced labour, and human trafficking.  

Unfortunately, it remains a persistent problem here in the UK. It’s an issue that affects men, women and children – across towns, cities and rural areas. Modern slavery arises when organisations or individuals disregard human rights in the name of profit, creating a trap for vulnerable people and forcing them to endure poor living and working conditions, and quite often physical harm, with little hope of escape. 

For UK main contractors, it imposes strict modern slavery compliance obligations, requiring thorough checks to ensure such practices are not present in their operations or supply chains. 

This blog covers: 

• What the Modern Slavery Act is 
• Who should comply 
• Why it matters in construction 
• Reporting requirements 
• How Constructionline helps main contractors avoid modern slavery and reputational consequences

 

What is the Modern Slavery Act 2015?

The Modern Slavery Act 2015 consolidates previous offences relating to trafficking and slavery. It introduced a requirement for large organisations to prepare a slavery and human trafficking statement annually.

Who should comply with the Modern Slavery Act? 

Section 54 of the Act, known as the ‘Transparency in Supply Chains’ clause, applies to any commercial organisation that: 

• Supplies goods or services. 
• Operates, wholly or in part, in the UK. 
• Has a total annual global turnover of £36 million or more.

Organisations meeting these criteria must publish a modern slavery statement outlining the steps taken to prevent modern slavery within their supply chain.

 

Reporting requirements under the Modern Slavery Act 

To comply, a modern slavery statement must be published on the organisation’s website with a prominent link on the homepage. While the Act does not prescribe the format, Government guidance¹ suggests content that may be included: 

• organisational structure, its business and its supply chains  
• organisational policies  
• assessing and managing risk 
• due diligence in relation to modern slavery (including approach to remediation) 
• training 
• monitoring and evaluation (understanding and demonstrating effectiveness)

 

Modern Slavery in Construction: Why Main Contractors must take action

The construction industry faces significant risks of modern slavery due to its reliance on complex supply chains, temporary labour, and agency workers. 

Risks in the supply chain 

The fragmented nature of construction projects often means main contractors depend on multiple tiers of subcontractors. Without visibility beyond Tier 1, exploitative labour practices can slip through unnoticed. Failing to address this is not only an ethical failure but also a critical business risk.

 

Consequences of non-compliance

If proper due diligence is neglected, main contractors face serious consequences: 

• Legal penalties: Unlimited fines for criminal offences related to slavery. 
• Reputational damage: Scrutiny from the public and loss of trust. 
• Commercial exclusion: Many public sector contracts now require evidence of robust modern slavery compliance to tender. 
• Project delays: Illegal practices discovered mid-project can halt operations and lead to terminated contracts. 

 

Simplify your supply chain compliance with Constructionline

Managing a modern slavery-compliant supply chain in the construction industry requires data, visibility, and verification. Constructionline supports main contractors by reducing risk and simplifying supply chain and subcontractor compliance verification processes:

Streamlined supplier verification 

Outsource your subcontractor compliance verification to us! Constructionline makes pre-qualification easier by validating subcontractors against the Common Assessment Standard (CAS). This industry-approved standard includes targeted questions on modern slavery, right-to-work checks, and ethical employment practices. 

Save time finding compliant supply chain members 

With access to a network of 30,000+ verified construction subcontractors, including suppliers aligned with the Common Assessment Standard in our Gold and Platinum memberships. 

Constructionline enables main contractors to: 

• Identify compliant suppliers: Instantly find subcontractors aligned with your minimum supply chain requirements, where our question sets ask about suppliers’ Modern Slavery Act policies and practices. 
• Monitor supply chain health: Track suppliers’ compliance statuses in real-time. 
• Reduce risk: Ensure suppliers follow Building Safety Act requirements, environmental guidelines, and modern slavery laws. 

 

Get better visibility of your supply chain’s compliance with the Modern Slavery Act 

Not sure where to begin? Discover more about our integrated construction and procurement supply chain software so you can: 

• Find verified suppliers 
• Filter by subcontractors who have a Modern Slavery Act statement 
• Demonstrate a strong commitment to ethical sourcing and legal compliance 
• Safeguarding your business and projects.  

 

FAQs 

Does the Modern Slavery Act apply to small construction firms?
The reporting requirement applies to businesses with a turnover of £36 million or more. However, smaller subcontractors are often asked to demonstrate modern slavery compliance when working with larger main contractors who must report on their supply chain. 

Our blog on how to avoid Modern Slavery might help you, as a supplier. 

What happens if a business doesn’t publish a Modern Slavery Statement?
Construction contractors can face grave damage to reputation if they don’t publish a Modern Slavery Statement, where some individuals or campaign groups may even ‘name and shame’. Avoid this by carrying out due diligence, making sure there is no slavery in your supply chain, and publish a statement. 

How does the Common Assessment Standard help with modern slavery compliance?
The Common Assessment Standard (CAS) replaces outdated schemes (like PAS 91) and includes specific modules on modern slavery, ensuring subcontractors have the necessary policies and checks in place. 

Learn more in our Gold and Platinum membership checklist.