A key Pentagon adviser is warning Australia that its next submarine fleet purchase may be obsolete as a result of game-changing technology breakthroughs in drone warfare.

Despite the intense political debate over procurement of submarines in Australia, former US military naval adviser and submarine expert Bryan Clark said he had not been contacted by Government officials here.

The Federal Government is planning to build a fleet of 12 new submarines, thought to be worth tens of billions of dollars.

Mr Clark told Lateline the next class of submarines would arrive in the 2020s, and said he did not know whether the Government was looking at the new detection technologies being developed.

"It is something that should impact the design of the next class of [Australian] submarines," he said.

"I've certainly been in contact with the US government in terms of what it might imply for how the next generation of US submarines needs to evolve."

Mr Clark said new technologies, particularly developments in acoustic techniques, meant quiet submarines could be easily detected by the enemy, rendering them ineffective.

"New detection techniques are emerging that would allow you to find large man-made objects in the water more easily than in the past," he said.

Mr Clark said the United States has relied on its submarines being undetectable and being able to operate with impunity in areas close to other countries, but "that is probably going to be coming to an end in the next 10-20 years with these new detection technologies".

When this happens, unmanned undersea vehicles would be used instead, Mr Clark told the ABC.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 8 minutes 24 seconds 8 m Bryan Clark talks to Lateline

He said submarines might still exist, but as mother ships to deploy these underwater drones.

"In the future we may find submarines, instead of being the fighter aircraft of the undersea world ... they may have to operate more like an aircraft carrier where they stay offshore some distance to stay away from the threat," he said.

"We will see a pull-back in terms of where we can operate submarines safely or with impunity and we will have to be deploying unmanned systems from submarines to get that last few hundred miles into the coast."

Limitations to unmanned systems, experts say

But with the advent of these unmanned undersea drone systems comes two limitations, Mr Clark said.

One is endurance, as they will be run on battery power. Another is a lack of accountability in terms of human control over weapons use.

"Even though you could autonomously program this to go and shoot a torpedo at a target it recognises, who will be accountable for the result if that hits a civilian ship instead of a military ship?" he asked.

Opponents of weaponised drones share this concern, and are warning that proliferation of new technology will hold untested risks for humanity.

Sheffield University artificial intelligence professor Noel Sharkey has founded a campaign called Stop the Killer Robots to change international law on military use of drones.

Professor Sharkey said governments were being driven by "getting a good edge on other countries".

"What happens when there is mass proliferation, what happens when there's an arms race, what happens when every technological nation has these?" he said.

He told the ABC that automated weapons were not fit for purpose in terms of general use and that they are unable to determine the difference between a civilian, or a combatant.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 9 minutes 19 seconds 9 m Noel Sharkey talks to Lateline

"We have to be very, very careful all the time," he said.

"Only a human can decide if an attack is proportional or not. If you have no human communication, how on earth can you be in control of what it kills?"

Professor Sharkey weighed in on the naval drone debate too, saying they would have to operate with minimal supervision by humans given the vast distances submarines usually travel.

"It will carry out the mission until you physically destroy it," he said.

"All governments need to look at how they will counter the unmanned drones from other countries."