Chris Keates, general secretary of the National Association of Schoolmasters Union of Women Teachers, described Marks & Spencer's "Blazer for iPod," which is part of the clothing manufacturer's 2008 Back to School collection, is "unnecessary and an error of judgment."

The blazer, which is available in both male and female styles, features an inside pocket for hidden electronic devices and hidden built-in controls compatible with iPods. The jacket also features lapels designed to conceal earphone wires.

"Teachers are already battling against the misuse of such technology in classrooms. Pupils nowadays come to school equipped with mobile phones, MP3 players, and portable games consoles when teachers would like them to just bring a pen," Keates said. "In its place this technology is useful, entertaining and perfectly legitimate for youngsters but its place is not for personal use in classrooms."