Paul McGarr, a delegate from East London, said that the union did not want to undermine servicemen and women but that the Forces were turning to schools to fill a recruitment shortage.

Mr McGarr said: “Let’s just try and imagine what recruitment material would have to say were it not to be misleading. We would have material saying, ‘Join the Army and we will send you to carry out the imperialist occupation of other people’s countries. Join the Army and we will send you to bomb, shoot and possibly torture fellow human beings.

“Join the Army and we will send you probably poorly equipped into situations where people will try to shoot or kill you because you are occupying other people’s countries. Join the Army, and if you come home, possibly injured or mentally damaged, you and your family will be shabbily treated.”

David Clinch, a teacher from Devon who joined the Royal Navy in 1967 on leaving school, where he had been a cadet, said that military cadet forces should be barred from schools because they were used for recruitment.

Martin Reed, of the NUT executive, said that teachers were by law required to treat political issues in a balanced way and to avoid partisan views. “It should be absolutely clear that the reality of war is demonstrated, not the marketised fiction of war,” he said.

Steve Sinnott, the union’s general secretary, has already written to Ed Balls, the Schools Secretary, to complain about a lesson plan produced for the MoD by an organisation called Kids Connections that, Mr Sinnott said, focused on “the ongoing occupation of Iraq by British Armed Forces”. A worksheet emphasised the Forces’ reconstruction work but, Mr Sinnott alleged, did not mention civilian casualties.

This year a Joseph Rowntree Trust report suggested that the Army was seeking to attract recruits by glamorising warfare and underplaying the risks involved in a military career.

Yesterday delegates at the union’s conference in Manchester voted in favour of a motion opposing military recruitment activities “based upon misleading propaganda”. The motion defended the rights of teachers “not to take part in activities promoting military recruitment, or which they feel present a partisan view of war and life in the military”. It said that young people should be able to “hear a speaker promoting alternative points of view” and to have “education for peace embedded in the curriculum along with education about the military”.

Mr Sinnott said he would convene a meeting of all parties involved, with a view to drawing up a protocol on recruitment. “I see nothing wrong in explaining to youngsters what life is like in the military, but you have to tell them the whole truth,” he said.

A spokesman for the MoD said that its recruitment practices avoided glamorising war and propaganda, adding that the Armed Forces did not recruit in schools and did not seek to attract youngsters aged under 16.

The Defence Dynamics initiative was not a recruitment activity, he said. The school material criticised by the NUT was part of a proposed English course on creative writing that included two articles, one positive about the Iraq conflict and the other critical.

“A career in the Armed Forces is not something to be ashamed of and we are proud to raise awareness of the tremendous work that our Service personnel do,” he said.