The UK Gambling Commission estimates that 2.5% of adults in Great Britain who had gambled online in the previous year used an illegal gambling website during the four weeks before the survey. Across all adults, including non-gamblers, the corresponding estimate was 0.6%. A further 1.5% of recent online gamblers reported use during the previous year but not in the latest four-week period.
How the index was built
The findings draw on four quarterly survey waves from April 2025 to April 2026, covering 14,257 online respondents and 3,569 people who had gambled online in the previous year. Indicators included using a site known not to be on Gamstop, signing up without age or identity checks, cancelling withdrawals and using a VPN to access an unavailable site. Only 128 respondents were classified as illegal-site users, a limitation the Commission highlighted.
Why the estimates are contested
Gambling Compliance International argued that consumer-reported incidence does not directly measure the share of gambling revenue captured by illegal operators. Its separate estimate put 2025 illegal online GGR in Great Britain at about £780 million. The two measures answer different questions, so operators and policymakers should avoid treating survey prevalence as a direct market-share estimate.