Some British governance and security experts say Australians should be sceptical about the claimed benefits of the new national security super-ministry.

Key points: Experts stress UK's Home Office is still not perfect after two centuries

Experts stress UK's Home Office is still not perfect after two centuries UK's national security hub regularly accused of being "unwieldy"

UK's national security hub regularly accused of being "unwieldy" Australia has been "comparing notes" with the British for "a while"

Prime Minister Malcolm Turnbull said the portfolio would be similar in style to the UK's Home Office, which oversees immigration, national security and law and order.

The Home Office, according to the UK experts the ABC spoke to, is a "functional" or "effective" model.

But they stress it evolved over more than two centuries and is not perfect.

"Certainly the UK's history on merging organisations makes you sceptical about the claimed benefits — I would look at that more than the Home Office model itself," said Julian McCrae, who served in the Prime Minister's Strategy Unit under Tony Blair and Gordon Brown.

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"Whenever you put things together in government, which we have done a lot … you generally see a performance dip in the next couple of years, while people get used to the new arrangements.

"The question is 'what's your rationale?' Is there enough long-term logic of bringing these things together to get over the short-term dip in performance, which is pretty much inevitable?"

Others, like retired Colonel Richard Kemp — a former Commander of British Forces in Afghanistan and former terrorism advisor at Downing Street — said there was "operational sense" in having spy agencies and police working closely together on national security matters.

But he did caution the Home Office is regularly accused of being "unwieldy".

"Sometimes that's a fair criticism, sometimes not," he said.

"On the whole the Home Office functions pretty effectively. Perhaps Australian officials have seen some benefit in the way it works.

"But it is one of the most controversial government departments and one that's often attacked mainly because its work affects so many people."

'We've been comparing notes on this'

Discussions with British officials on the Home Office model have been taking place for "a while", according to Australia's High Commissioner in London, Alexander Downer.

"We chat about these things. The British are very positive about how the Home Office as an institution works," he said.

"Given the Prime Minister's interest in this we've been comparing notes."

The idea of a new super-ministry has been discussed for many years in Canberra.

But Mr Downer, who was Australia's longest-serving foreign minister, would not say whether he personally supported the idea.

"I'm a public servant, I don't have a personal view," he said.