Online retail companies should ban the sale of mini mobile phones designed to be smuggled into prisons, said justice secretary David Lidington on Monday. From a report: Often marketed as "Beat the Boss phones", the tiny feature phones can be bought for around $25 to $40 online on sites including Amazon, Ebay and Gumtree. On the inside, they can change hands for up to $670. The phones, which can be as small as lipsticks, are popular with prison inmates due to their discreet size and lack of metal, which allows them to beat metal detectors. Mobile phones are banned in prisons, in part because they allow inmates to continue criminal activities while they're locked up. But around 20,000 phones and SIM cards were seized by prison guards in 2016, with mini mobiles making up around a third of these.