Staff in mobile phone shops have become key to the execution of "Sim swap" scams, Watchdog Live has discovered. Undercover filming revealed that O2 and Vodafone employees are bypassing basic ID checks and handing over replacement Sim cards to potential criminals. Once fraudsters gain control of a mobile number, they can intercept SMS text messages from banks containing security codes.

Scammers have drained thousands of pounds from victims' bank accounts.

O2 told the BBC it currently only asks for photo ID when replacing Sims on a monthly contract, and that customers on Pay As You Go contracts would always receive an authorisation code alerting them that someone is trying to access their number. However, that did not happen with any of the numbers being used by the Watchdog Live team, who were able to walk out with a replacement Sim in almost every case. O2 says it did send out authorisation codes, but they were not received by the victims' smartphones. Vodafone said that it takes Sim swap fraud "extremely seriously" and that it is disappointed that two of its employees did not follow established security check procedures, despite being given mandatory training, reinforced by regular reminders to the contrary.