The Bay of Plenty District Health Board has taken a dispute over a midwives' strike to the Employment Relations Authority (ERA).

The DHB has claimed strike action created a dangerous situation at Whakatane Hospital's maternity unit by failing to provide life-preserving services, which the union denied.

The complaint refers to a two-hour strike held on Saturday November 24.

Union co-leader Caroline Conroy said the complaint was "completely unnecessary" and had the potential to derail the relationship between midwives and management.