It was immediately obvious that Melbourne tour guide Tom Malone's question to Curious Canberra closely resembled the American political drama Designated Survivor.

The show is based on a low-level Cabinet member becoming president of the United States after an explosion in Washington kills everyone above him in the line of succession.

A visitor on one of his tours, which cover how Federal Parliament was held in Victoria between 1901 and 1927 while Canberra was being built, asked whether Parliament moves back to Melbourne or elsewhere if it is attacked.

"So I thought 'Why not ask Curious Canberra?'" he said.

"I'm delegating [it] to the ABC, because you guys aren't already stretched enough," he added tongue-in-cheek.

In the US TV show, one Cabinet member is removed from major events in case of emergency and earmarked as the "designated survivor". From there it's underground bunkers, secret tunnels and escorted motorcades.

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But if that happened in Australia, would Parliament move interstate or be rescued by an underground bunker?

What we know:

Australian governments have previously been rapped over the knuckles for not having any national emergency plan.

A 2008 review into homeland and border security by former defence secretary and ambassador Ric Smith found:

"While crisis management by the Commonwealth has generally been done well 'on the day', the current hazard-specific approach and the absence of consistent national arrangements for handling significant crises exposes the Government to several areas of vulnerability."

So, we called the Department of Parliamentary Services to see if anything had changed.

Understandably, a spokeswoman was tight-lipped about parliament's emergency plan, except to reassure us one exists.

"A comprehensive plan is in place to ensure the effective continuity of Parliament in the event that an emergency renders Parliament House unusable," she said.

And the 2009 federal budget revealed $7.4 million was spent on a plan to protect the nation's decision makers in such emergencies, with details again shrouded in secrecy.

Rumours and theories

Curious Canberra previously discovered a tunnel beneath Old Parliament House, but it is narrow and muddy. ( ABC News: Sonya Gee )

Canberra historian Dr Peter Dowling believes where government sits in an emergency would depend entirely on the event.

He said if Parliament House was partially compromised, politicians could create a makeshift meeting area in the basement of Parliament House, like how Winston Churchill's government constructed Cabinet war rooms beneath the Treasury building during WWII.

But Dr Dowling said if Canberra was compromised, a section of government could move to Sydney or Melbourne.

"Let's say if Canberra was completely burnt out and gutted and absolutely cut off from the rest of Australia — from some type of warfare or natural disaster — they would have contingency plans available to make a sort of parliamentary and decision making group," he said.

ABC national affairs correspondent Greg Jennett agreed a makeshift cabinet would be formed in the event of an emergency, but theorised it would be a government of national unity — where the opposition leader and key frontbenchers were included in decision-making.

And while noting he was speculating, he was sceptical those meetings would happen in Parliament House's basement.

"We do know there are facilities somewhere — but in this day and age it's got to have secure communications," he said.

"It's unclear to me that there's any room in the basement of Parliament House that would fit the bill.

"And if there was a bunker, and it was maintained, cleaned, serviced, and had its communications checked, you would know about it right? Because there's a number of people who work in this place and the secret would have gotten out!"

Federal parliament sat in Melbourne between 1901 and 1927 while Canberra was being built. ( National Library of Australia nla.pic-an23312255 )

He also noted that forming cabinet would not necessarily be required, as many laws for emergencies already exist.

"In the Defence Act there are already very strong powers embedded, as there are in sections of our health legislation," he said.

"Say we were attacked with some biological agent — the chief health officer can invoke all sorts of restrictions.

"They have powers to quarantine us, restrict our movements and administer antidotes to us."

'If I told you, I'd have to kill you'

Professor John Blaxland heads the Australian National University's Strategic and Defence Studies Centre.

He warned he'd have to kill us if he revealed the contingency plans he knew existed.

"And then of course if I told you the details they'd have to kill me too," he said half-jokingly.

John Blaxland used to work at Joint Operations Command and said it wasn't a suitable location to convene parliament. ( Supplied: ANU )

He was also quick to throw cold water on the theory of purpose-built bunkers and secret underground tunnels.

"You really have to go to North Korea to get the experts of bunkers and tunnels — we're not that good at it in Australia," he said.

And he dismissed suspicions the Joint Operations Command (JOC) headquarters to Canberra's east, which he labelled a "big barn above ground," would be suitable for Parliament.

"It's just not designed for that," he said.

"You can run a crisis contingency planning group from there, but essentially you'd have to look for somewhere else."

Bomb shelter included in original plans for Parliament House

Cabinet documents from 1981 talk about a space underneath Parliament House reserved for emergencies. ( National Archives of Australia )

Cabinet documents from 1981, released 30 years later, revealed a custom-built bomb shelter for Parliament House was abandoned during the building's planning because its $1.8 million bill was deemed too expensive.

Instead, the Fraser government set aside a large bunker in the basement to convert to a bomb shelter in the future, and planned to use the underground car park in the event of a nuclear attack.

Following the documents' release, then-secretary of the Department of Parliamentary Services Alan Thompson told Fairfax Media the cabinet submission reflected security concerns held ''at the height of the Cold War'' and that he was not aware of any area reserved in Parliament House's basement for a potential nuclear war.

However, he did concede that Parliament House had enough underground space to house a bomb shelter, including "The Cathedral" — a vast space carved into the rock of the hill under the House.

In the event of a nuclear attack...

Professor Blaxland told us Parliament House staff prepare for floods and fires like any other office workers around the country.

But he admitted the plan for politicians in a more serious emergency would depend on the incident.

"If you're facing a nuclear bomb going off over Parliament House, well then you're going to face the radiation of most of the central core of Canberra, which rules out everything in that area and you've got to look further afield," he said.

"But essentially there are a range of options to choose from depending on where the prime minister is, how many people have died in the explosion or incident [and] whether or not there's a need to convene parliament at all or if you can hold off for a while."

President Barack Obama meets in the Situation Room with his national security advisors in 2013. ( White House: Pete Souza )

He also warned that differences between the Australian and US political systems meant a "Designated Survivor scenario" was unlikely, adding the Governor-General would have to be alive to swear in a new prime minister.

Though he said Australia's security agencies did require plans to prepare for a government attack, along with the rest of the world.

"With the advent of Kim Jong-un and his intercontinental ballistic missiles, it actually starts to become mildly plausible that something dramatic might happen to us," he said.

"Now the probability remains extremely low that Kim Jong-un could not only get the missile to fire accurately, but with the right warhead on it to do any damage.

"So I'm actually pretty relaxed about all this, I don't lose much sleep worrying about it. But it's good to know that some people out there are giving it some thought and coming up with contingency plans — just in case."