A radical reorganisation of national security agencies, such as the creation of a US-style department of homeland security is not necessary because existing arrangements are working well, experts and former officials say.

Top experts took the view that there was no compelling reason for such a dramatic overhaul after Fairfax Media reported that the Turnbull government was considering creating a super-department like that set up in the US after the September 11, 2001 attacks.

Peter Varghese, former head of both the Department of Foreign Affairs and the Office of National Assessments, said that if there had been "an obvious deficiency" then it would make sense to look at alternatives but the present system "works pretty well".

"I don't think there's a compelling reason to look at a radical change," he said.

Mr Varghese said a super-department at the federal level would not necessarily improve co-ordination with state agencies, which came under scrutiny for instance in the Lindt Cafe siege.

"If you are looking at federal-state relationships, I'm not sure a department of homeland security would be a solution," Mr Varghese said.

Ric Smith, a former Defence Department head and senior diplomat who led a review of homeland security in 2008, said a large, new department would not necessarily improve co-ordination and carried its own risks of increased lethargy.

"I recommended against this [one large department] in 2008 because I considered that maintaining smaller, fully accountable, more nimble organisations that are thoroughly well-joined up was a better way to go," he said.

"That remains my view. The emphasis has to be on ensuring they are well-connected."

Peter Jennings, a former senior Defence official and now executive director of the Australian Strategic Policy Institute, expressed a similar view, saying the Turnbull government should take a conservative approach to any changes.

"What's broken?" he said. "I don't get the impression that co-ordination on counter-terrorism is a problem right now. I think our system is working very well."

Under the homeland security plan that is under consideration, agencies that deal with national security, including ASIO and the Australian Federal Police, would be taken out of the Attorney-General's portfolio and instead fall under the new super-department that would be responsible for border security, domestic counter-terrorism and federal law enforcement. It would be comparable to Britain's Home Office or the US Department of Homeland Security.

The plan is being pushed by Immigration Minister Peter Dutton and the Secretary of his department Mike Pezzullo, Fairfax Media understands. Prime Minister Malcolm Turnbull on Tuesday sidestepped a question about the overhaul.

It is understood the relevant agencies are not in favour of such a sweeping change.

A less radical alternative would be to alter cabinet portfolio responsibilities, perhaps creating a senior minister for national security and counter-terrorism.

But to take this responsibility away from the Attorney-General could cause difficulties, given the Attorney-General as the nation's first law officer signs ASIO warrants and provides oversight of their sometimes extraordinary powers. Several past reviews have recommended against this.

Australia has had four incidents defined by the government as terrorist attacks since September 2014 when the alert level was raised to "probable". Over the same period, 57 people have been charged as a result of 25 counter-terrorism operations.

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