Britain's biggest teachers' union has accused the Ministry of Defence of breaking the law over a lesson plan drawn up to teach pupils about the Iraq war. The National Union of Teachers claims it breaches the 1996 Education Act, which aims to ensure all political issues are treated in a balanced way.

Teachers will threaten to boycott military involvement in schools at the union's annual conference next weekend, claiming the lesson plan is a "propaganda" exercise and makes no mention of any civilian casualties as a result of the war.

They believe the instructions, designed for use during classroom discussions in general studies or personal, social and health education (PSE) lessons, are arguably an attempt to rewrite the history of the Iraq invasion just as the world prepares to mark its fifth anniversary.