The devices, which enable Taliban fighters to detonate bombs by remote control, are either sent to sympathisers in neighbouring countries or carried in by volunteers who flew to Pakistan and crossed the border into Afghanistan, a report claimed.
Details of how British electronic components had been found in roadside bombs were given to David Miliband, the Foreign Secretary, when he visited British troops at their military compound at Lashkagar, in Afghanistan, this week.
In a briefing on operations by Brig Gordon Messenger, the Royal Marine commander of the British battlegroup, Miliband was shown samples of the home-made devices that were being used in attacks.
They included mobile phones filled with explosives used to attack foot patrols and more powerful devices used against vehicles.