The "Blazer for iPod", which is part of the shop's 2008 Back to School collection, has been branded irresponsible by the NASUWT.

The organisation is concerned the new jacket, which has built in controls and hides the ear phone wire in the lapels, will encourage youngsters to flout school rules by listening to music in class.

"This is unnecessary and an error of judgement," General Secretary Ms Chris Keates said.

"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.

"In its place this technology is useful, entertaining and perfectly legitimate for youngsters but its place is not for personal use in classrooms.

The blazer, available in boys and girls styles, features an inside pocket and five function keypad controller built into the lapel area of the lining.

This enables the child to play, pause, fast forward and rewind tracks on their iPod and has lapel loops that conceal the earphone wires.

M&S claim the eco-friendly blazer, which is made from fabric produced by recycling plastic bottles, is perfect "for music on the move".

But Ms Keates said it helps children break the rules.

"Apart from the distraction from learning, the misuse of technology such as mobile phones to bully and harass pupils and staff and the loss, breakage or theft of these items places additional burdens on teachers," she said.

"Such is the scale of the problem the NASUWT has been running a major campaign to secure government backing against the misuse of technology in schools and many schools have found it necessary to develop policies on this issue.

"Most of these prohibit such items being brought into the classroom or even into school. Providing pockets in school uniform specifically designed to conceal these items is tantamount to legitimising the flouting of school rules.

"Some youngsters already have little problem in doing this. They don't need to be aided and abetted by businesses using such gimmicks to give their uniforms the edge over their competitors."

Parents also seemed sceptical about the new uniform.

Hayley Hamlett, 38, whose 15-year-old daughter Sherri is a head girl at Hamble Community Sports College, Hants, , said: "It sounds horrendous and it encourages anti-social behaviour and children to listen to music in lessons.

"Many adolescents seem to walk round unable to hear what's going on a lot of the time anyway because they have earphones in and this encourages that.

"My daughter Sherri might love it but there's no way I would buy it for her.

"At her school they do not like children taking any valuables in, whether they are phones or iPods, and this would seem to encourage them to break school regulations."

The blazer, which is black and comes in sizes from age 10 to age 16, costs £25 to £30.00.