The Government chose not to hold a public inquiry into the attack on Sydney Harbour. Instead, Rear Admiral Muirhead-Gould provided a preliminary report to the Government of the attack on 22 June, and a final report on 16 July. Both reports continued the claim that there were four midget submarines in the harbour, when in fact there were only three. This was attributed to the confusion surrounding the events in Taylors Bay, the number of vessels involved in the action, and the initial interpretation of four crossings recorded on the Indicator loop.
Japanese records confirm there were only three midget submarines deployed into Sydney Harbour in May 1942.
The deficiencies in the defence system on the night of the attack were identified as the failure of the outer indicator loop; the failure of the operators to recognise the midget crossings; communications, including the reliance on light signals between vessels, and between vessels and Garden Island, rather than wireless transmitters and telephones; the lack of a completed anti-submarine boom net, and the absence of depth charges on the naval auxiliary patrol boats.