Classroom teaching unions are among 30 organisations that have complained to the Health Secretary about plans for firms such as Mars, Cadbury and Coca-Cola to fund anti-obesity campaigns. In a letter to Andrew Lansley, the groups condemned his aims, saying they are a threat to the health of British children. It added: “Voluntary approaches have repeatedly been shown to be ineffective and we would be deeply concerned if the coalition Government were to rely on industry self-regulation.”