Modern Slavery in Construction: What Contractors Need to Know

Why construction is high risk

The Global Slavery Index and UK government risk assessments consistently identify construction as a high-risk sector for labour exploitation. Several structural features of the industry create this risk:

• Complex, multi-tier supply chains: labour can be several steps removed from the Principal Contractor, making due diligence difficult
• High use of labour agencies and gangmasters: workers may not know who their legal employer is
• Prevalence of migrant workers: language barriers and unfamiliarity with UK employment law can increase vulnerability
• Cash-in-hand and informal payment practices in parts of the sector make payment monitoring difficult
• Seasonal and project-based work: short contracts and frequent changes of site can obscure patterns of exploitation
• Remote and temporary sites: accommodation arranged by the employer can create dependency

The Home Office's Construction Protocol and the Gangmasters and Labour Abuse Authority (GLAA) have identified construction as a priority sector for enforcement.

The Modern Slavery Act 2015

The Modern Slavery Act 2015 consolidates and extends previous legislation on trafficking and forced labour. It creates two categories of relevance for construction employers:

Criminal offences (all employers)

Regardless of company size, it is a criminal offence to:

• Hold a person in slavery or servitude (Section 1)
• Require a person to perform forced or compulsory labour (Section 1)
• Traffic a person for labour exploitation (Section 2)

A person convicted of a Section 1 or Section 2 offence can receive an unlimited fine and up to life imprisonment. Employers who knew or ought to have known that their supply chain involved forced labour can face prosecution.

Transparency in supply chains (larger businesses)

Section 54 of the Act requires commercial organisations that supply goods or services in the UK and have an annual global turnover of £36 million or more to publish an annual slavery and human trafficking statement. This statement must be:

• Approved by the board of directors (or equivalent)
• Signed by a director (or equivalent)
• Published on the company website within 6 months of the financial year end
• Accompanied by a prominent link to the statement from the company homepage

What the annual statement must cover

The Act specifies six areas that the statement may cover. The Home Office expects stronger statements to address all six:

Area	What to include
Organisation structure and supply chains	How the business is structured, what it does, and the nature of its supply chains - including tiers
Policies	Modern slavery policy, whistleblowing policy, supplier code of conduct, recruitment policy
Due diligence	How you check suppliers, what questionnaires or audits you use, how you respond to concerns
Risk assessment	Which parts of your business or supply chain carry the highest risk and why
Key performance indicators	What you measure - e.g. proportion of supply chain audited, number of concerns reported, training completion rates
Training	Who receives training, what it covers, how frequently it is updated

Weak or generic statements are actively criticised by the Home Office, GLAA, and NGOs. Several large contractors have been publicly named for failing to publish a statement or for publishing a statement that is clearly inadequate.

Warning signs on site

Supervisors and site managers should be trained to recognise these indicators. They do not individually prove exploitation, but clusters of indicators warrant investigation.

Worker behaviour indicators

• Workers who appear fearful, confused, or unable to speak freely - especially when a third party is present
• Workers who defer to one person who answers all questions on their behalf
• Workers who do not know their employer's name, address, or pay rate
• Workers who seem unaware of UK employment rights
• Workers who appear malnourished, exhausted, or show signs of physical abuse

Attendance and movement indicators

• Workers collected and dropped off at exactly the same time by the same vehicle or person
• Workers who are never seen outside working hours - no breaks, no independent movement
• Workers living on or near the site in overcrowded accommodation arranged by the employer or labour provider
• Workers whose personal identity documents are held by a third party

Payment and employment indicators

• Wages claimed to be paid to a bank account in someone else's name
• Workers who believe they must work excessive hours to "pay off a debt" to their employer or recruiter
• Workers who have paid a recruitment fee - fees to workers are illegal in the UK
• Workers without written contracts or payslips
• Workers who are working for multiple labour providers simultaneously without apparent awareness

Supply chain due diligence

Principal Contractors are responsible for the conduct of their supply chain. Your due diligence approach should be proportionate to the risk, with higher scrutiny for higher-risk relationships (e.g. labour-only subcontractors, gangmaster arrangements, international recruitment).

Pre-qualification

• Require all subcontractors to complete a PQQ that specifically addresses modern slavery and labour exploitation
• Ask for copies of their own modern slavery statement if their turnover exceeds £36 million
• Ask which labour agencies they use and verify that those agencies are licensed by the GLAA where required
• Check Companies House for recent incorporations and sole director structures that may indicate labour supply chain risks

Contractual requirements

• Include a contractual obligation requiring subcontractors to comply with the Modern Slavery Act
• Require the obligation to flow down to sub-subcontractors (back-to-back clauses)
• Include a right to audit clause - the right to inspect records and interview workers at any time
• Include a termination right for breach of modern slavery obligations

On-site checks

The most effective operational checks that Principal Contractors can run:

• Right to work checks on every worker: not just an identity check, but a verified right to work check following the Home Office process. Workers with no right to work are at much higher risk of exploitation.
• Attendance verification: confirm that workers who appear on payroll were actually present on site. Discrepancies between claimed attendance and actual attendance are a strong indicator of payroll fraud and potential exploitation.
• Induction process: use the site induction to explain workers' legal rights - what they are entitled to be paid, that they have a right to keep their own documents, and how to report a concern.
• Spot checks on subcontractor workers: supervisors should be trained to conduct informal conversations with subcontractor workers to check welfare.

The GLAA Construction Protocol

The Gangmasters and Labour Abuse Authority (GLAA) has published a Construction Protocol developed with industry, setting out minimum standards for managing labour exploitation risk on construction sites. Key elements include:

• Requiring all labour providers to hold a GLAA licence where required by the Gangmasters (Licensing) Act 2004
• Implementing payroll verification to confirm workers are paid directly and at the correct rate
• Providing workers with information about their rights in their own language
• Establishing a site welfare contact who workers can approach confidentially
• Training all site managers and supervisors to identify and respond to indicators

How AttendIQ supports modern slavery compliance

Modern slavery monitoring relies on knowing who is actually on site, verifying their right to work, and maintaining records that can support both internal audits and GLAA investigations. AttendIQ provides:

• Right to work checks: document upload and expiry tracking for all workers, with access blocked for workers with expired or missing right to work status
• Attendance verification: GPS clock-in/out with a live FILO board - cross-reference actual attendance against claimed attendance from labour providers
• Induction tracking: confirm that every worker has completed the site induction, including any modern slavery awareness content you include
• Supply chain visibility: see all workers on site by their employing organisation, making it easier to identify patterns that warrant investigation
• Automated detection: AttendIQ's modern slavery detection module flags attendance patterns consistent with exploitation indicators - such as workers with no independent clock-in/out variation across long periods
• Audit trail: full records of who was on site, when, and their compliance status - available for GLAA inspections or internal audits