The Defence Industry Association says it kept its annual conference deliberately low-key to avoid protests.
About 120 manufacturers, mainly from New Zealand, attended the event.
The association's administration manager, Fraser Boyd, says the meetings are never publicly advertised, because they are designed for a limited number of people with an active interest in the industry.
However, the co-ordinator of Peace Movement Aotearoa Edwina Hughes says the level of secrecy is not warranted where public money is involved.