The UK’s data watchdog has warned hundreds of online gambling affiliates to lay off the spam messages or face the consequences.

On Thursday, the Information Commissioner’s Office (ICO) posted a notice saying it had written to over 400 companies it believes are improperly using individuals’ personal details to promote gambling services via text messaging services.

David Clancy, the ICO’s anti-spam investigations manager, said his group was prompted to act after receiving complaints from customers who were subjected to unwanted gambling promo offers from affiliates. Clancy said the ICO was also acting on “intelligence from other sources.”

The ICO said it has become aware of “particular problems around affiliate marketing” in the gambling sector. In many cases, neither gambling operators nor their affiliates were “taking any responsibility for complying with the rules” regarding personal data misuse. Clancy said “not knowing the law or trying to pass the buck to another company in the chain is no excuse.”