HMAS Collins transits through Cockburn Sound at sunrise.

HMAS Collins transits through Cockburn Sound at sunrise. Photo: Supplied

Australia's Collins class submarines would almost certainly be blown out of the water if they were sent into action against the modern submarines that will be operating in the region from the 2020s, says the man who built them.

Hans Ohff, the original managing director and chief executive officer of the Australian Submarine Corporation, told The Canberra Times claims the vessels could be kept operational until 2035 are absurd.

Mr Ohff oversaw the delivery of the six Collins class boats between 1996 and 2003.

He also says current Australian Submarine Corporation chief executive Steve Ludlam's recent claim the existing boats could be kept operational without new engines is a flight of fancy.

The managing director and chief executive officer of the Australian Submarine Corporation from 1978 to 1992 and the chairman of Australian Submarine Corporation's engineering services until 2002, Mr Ohff said while the Collins was brilliant in its day, the 1980s design had since been overtaken by three new generations of submarines.

''I am very proud of what we achieved [with Collins] but if one of those went up against a modern submarine such as a German HDW 209 or 214, I would rather be in them,'' he said. ''By 2035 you might just as well stay in port - you'd get blown out of the water [if you put to sea].''

Mr Ohff backs a ''military-off-the-shelf solution'' to be developed in partnership with a European submarine company. If the future submarines can't be built in Adelaide for less than $1.5 billion each they should be built overseas.

Australia's most successful submarines, the O-Boats that were in service from 1967 until 2000, were a classic ''military-off-the-shelf solution'' (see graphic).

Mr Ohff likened trying to keep Collins's notoriously unreliable diesels in operation for another 23 years to maintaining a vintage car.

''Collins doesn't have the diesels it should have had from the start; it [the engines] aren't a good fit for a submarine,'' he said. ''You could run the diesels for another 100 years but they are never going to be the best solution - they will always be less quiet and less reliable than they should be. It wouldn't be efficient.'' He poured cold water on the current push by the Australian Submarine Corporation, Defence Minister Stephen Smith and Defence Materiel Minister Kim Carr and a Defence faction to keep Collins alive and well until 2035 to allow the development of an ''evolved Collins'' that would be designed and built in Adelaide.

The Australian Submarine Corporation is lobbying hard for this option, even though it is not known if the life-extension is possible, what it would cost (if it can be done) and how long it would take.

Senator Carr, also the minister for manufacturing, came close to endorsing this approach outright at the Australian Defence Magazine Congress in Canberra last week.

''Defence procurement is not simply about buying modern weapons; it's very much a part of developing a modern country,'' he said.

''Why shouldn't we support our troops by investing in ourselves? We simply cannot rely upon someone else to do all the jobs that we can't do ourselves.''

Mr Ludlam, who hit out at media criticism of the ''evolved Collins'' model at the conference, conceded it was taking up to one million man hours to carry out deep maintenance on the boats, which he claimed had taken 2.5 million man hours each to build. Mr Ohff said that figure was not correct.

Mr Ludlam was unable to say how long a life extension program to add 10 years service to the Collins would take.

Mr Ohff said an ''evolved Collins'' would lock Australia into outdated design principles.

''There is not sufficient flexibility in the Collins class design,'' he said.

At least two or three Collins should be retired sooner rather than later to allow the sustainment effort to be concentrated on the remaining boats.

While this was happening a commercial partner for the design and construction of the new fleet should be sought.

The future submarine should weigh about 3500 tonnes, come with air independent propulsion, the latest hull shape, engine technology and sensor suite.

Mr Ohff said the new vessels should be based on a current European design, such as a German HDW 214, and could be built in Australia for about $1.5 billion per vessel.