Facebook's UK chief has been asked to turn the company's biometric tech on users breaking the law.At a questioning, Facebook chief Mike Schroepfer was asked by Facebook doesn't use the facial recognition technology it already has to block fake adverts.The social media giant's chief technical officer was questioned by MPs in the UK about the firm's impact on politics.Earlier this week, Martin Lewis, founder of the consumer help site MoneySavingExpert.com, said he would sue Facebook for defamation over fake adverts”We are investigating ways to do that,” says Schroepfer. “It is challenging to do at scale.”