Exaggerated fears over safety risks are causing hundreds of thousands of children to miss out on school trips vital to broadening their education, the film producer and education adviser Lord Puttnam warned yesterday. Speaking at the launch of a National Trust education campaign to promote learning beyond the classroom, the peer branded as "barking" excessive safety concerns whipped up by the media. Mounting alarm over the past five years over school trips and safety was "one of the greatest single problems confronting current educational practice," he said. "Somehow we have got to get past it."

Lord Puttnam spoke as the trust unveiled research showing nine out of 10 teachers believe pupils go on too few school visits. The trust hosts 500,000 children on school trips each year and argues that its wealth of land and properties, ranging from stately homes to workhouses, justifies its claim to be "the nation's biggest classroom". It warned that "out of classroom learning is being relegated to an optional, unfunded add-on to classroom-based studies". Teachers surveyed said their main concern over school visits was health and safety, although the trust's director general, Fiona Reynolds, said schools were also limited by budgets and timetables.

The trust took a robust approach to health and safety without "sanitising" its attractions, she said. "We do live and work in an environment in which there is always an element of unpredictability and inherent risk. "But I also believe passionately that if we were to take that risk away we would utterly destroy everything that we stand for." Guidance for schools and school holiday operators has been tightened in recent years following a number of tragedies, mainly on adventure trips. However, the National Association of Schoolmasters-Union of Women Teachers last year became the first to advise its members against trips. It warned that there had been 11 deaths and 7,000 "near misses" on school trips over the preceding three years.