During the s, the RAN began plans to replace the River-class destroyer escorts based on the British Leander -class frigate with a mid-capability patrol frigate and settled on the idea of modifying a proven German design for Australian conditions. Around the same time, the RNZN was seeking to replace their Leander -class frigates while maintaining blue-water capabilities.
As both nations were seeking warships of similar capabilities, the decision was made in to collaborate on their acquisition. Twelve ship designs were tendered in The frigate acquisition was controversial and widely opposed in New Zealand, and as a result, the additional ships were not ordered. The armament initially consisted of a single 5-inch gun and a point-defence missile system, supported by a missile-armed helicopter.
In addition, the ships were fitted for but not with a torpedo system, anti-ship missiles , and a close-in weapons system. The last ship of the class entered service in ; by this point, the RAN and RNZN had embarked on separate projects to improve the frigates' capabilities by fitting the additional weapons, along with updates to other systems and equipment. Around the same time, the need to replace the RNZN's Leander -class frigate force with new warships was under consideration.
However, it became clear that surface vessels were also required and the cost risk was too high. Alternate suggestions, such as reducing the RNZN to a coast guard -type force responsible for coastal and fisheries protection, replacing the frigates with smaller offshore patrol vessels , or reorienting the navy to primarily operate submarines, were made in several venues, but were seen as an unacceptable loss in capability.
On 6 March , a Memorandum of Understanding was signed by the two nations and RNZN representatives were invited to collaborate on the project. When the time came to commit, they could either continue cooperating into the construction stage of the project, independently order the ships from the designer or abandon the project entirely. In , the Australian Force Structure Review contained plans to replace the three Perth -class guided-missile destroyers and four of the six Adelaide -class guided-missile frigates with air defence vessels.
