In 1938, the
Australian Commonwealth Naval Board (ACNB) identified the need for a general purpose 'local defence vessel' capable of both anti-submarine and mine-warfare duties, while easy to construct and operate. The vessel was initially envisaged as having a
displacement of approximately 500 tons, a speed of at least , and a range of The opportunity to build a
prototype in the place of a cancelled
Bar-class boom defence vessel saw the proposed design increased to a 680-ton vessel, with a top speed, and a range of , armed with a 4-inch gun, equipped with
asdic, and able to be fitted with either
depth charges or
minesweeping equipment depending on the planned operations: although closer in size to a
sloop than a local defence vessel, the resulting increased capabilities were accepted due to advantages over British-designed mine warfare and anti-submarine vessels. Construction of the prototype did not go ahead, but the plans were retained. The need for locally built 'all-rounder' vessels at the start of World War II saw the "Australian Minesweepers" (designated as such to hide their anti-submarine capability, but popularly referred to as "corvettes") approved in September 1939, with 60 constructed during the course of the war: 36 ordered by the RAN, 20 (including
Ballarat) ordered by the
British Admiralty but manned and commissioned as RAN vessels, and 4 for the
Royal Indian Navy.
Ballarat was laid down by
HMA Naval Dockyard in Williamstown, Victoria, on 19 April 1940. She was launched on 10 December 1940 by the wife of
Albert Dunstan, then
Premier of Victoria, and commissioned into the RAN on 30 August 1941. ==Operational history==