The General appointed to fix Australia's faltering COVID-19 vaccine rollout has been named for another challenging job back in Defence, but it remains unclear when he will be able to begin his new role.

Lieutenant General John Frewen will take on the position of Chief of Joint Capabilities (CJC), as the Defence Force establishes a high-powered taskforce to examine how Australia can best acquire submarines with nuclear propulsion.

In June, Prime Minister Scott Morrison asked General Frewen to take on the role of Coordinator General of the National COVID Vaccine Taskforce, reporting directly to him and Health Minister Greg Hunt.

The appointment of the widely respected Army figure to head Operation COVID Shield has drawn some criticism over concerns it could politicise the military.

The Australia Defence Association in July tweeted: "Relying on the ADF to head emergency efforts (not just assist the civil community) risks dragging a necessarily non-partisan institution into #auspol controversy."

Correspondence released under freedom of information laws this month show Mr Morrison told General Frewen "the necessary resources and assets will be put at your disposal" to help speed up COVID-19 vaccinations in Australia.

The ABC has confirmed the three-star General's next appointment back in Australian Defence Force Headquarters formally begins this month, but military colleagues have not yet been told when he will arrive.

An internal Defence notice circulated late on Monday states "he will remain seconded to the Department of Health as Coordinator-General of the National COVID Vaccine Task Force until his duties in that role are complete".

General Frewen takes over as CJC from Vice-Admiral Jonathan Mead, who has been appointed to the newly created position Chief of Nuclear Powered Submarine Task Force.

Task force to choose nuclear submarine

Senior officers and officials have also been announced for the newly established Nuclear Powered Submarine Task Force, which will be headed by Vice-Admiral Mead.

The powerful grouping is noticeably separate from the Defence Department's Capability and Sustainment Group (CASG), which is usually responsible for all the ADF's military equipment and supply requirements.

Vice-Admiral Mead was instrumental in Australia's top-secret efforts this year to identify possible options for nuclear-powered submarines instead of the now cancelled $90 billion French designed conventionally future fleet.

"Commensurate with the Government's announcement of the Nuclear Powered Submarine, a new three-star position will lead the Task Force," an internal notice from Defence Chief General Angus Campbell confirms.

From next year, General Campbell will have a two-star officer, Major-General Christopher Field, serving him in the newly established and temporary position of Assistant to Chief of the Defence Force, but it is unclear precisely what the role involves.

By the end of 2021, the Royal Australian Navy Commodores will also be dispatched to the United Kingdom and the United States to serve as Nuclear Powered Submarine Task Force Liaison Officers.