Retailers Marks and Spencer are using technology to secretly track people’s movements via their mobile phones.

Devices installed in the ceilings of M&S stores pick up the signals sent out by shopper’s mobile phones as they search for Wi-Fi connections, signals that can be used to pinpoint a shopper’s position. This information can then be used to count the number of people who visit a store, and what parts they visited, so that store layout can be altered to sell more M&S goods. The technology can also be used to bombard phone users with advertisements. Shoppers who don’t want this are being advised by privacy campaigners to turn off their phone’s Wi-Fi and Bluetooth capacity when shopping.

M&S have also come in for criticism, and customer loss, over the heavy-handed demands of M&S Bank for existing customer, some of whom have had an M&S card since the Eighties, to prove their identity. This, M&S demand, is by providing documents such as passports, household bills or driving licences and verification that the documents are genuine by a professional worker who knows them, who in turn has to provide, along with their name and address, their occupation, employer’s name and address, phone number, signature and professional registration number. Some M&S customers, who say the retailer has lost the plot, have been asked to travel a hundred miles to produce the proof at a branch.