The Submarine Institute of Australia (SIA) has defended the development of Australia’s Future Submarine based on the Naval Group nuclear-powered Barracuda.

Responding to calls to ditch the Barracuda-based design and instead buy an “off-the-shelf” design the president of the SIA, Mark Sander said Australia has a positive plan in place for the Future Submarine Program.

“A competent and professional designer partner and combat systems integrator have been selected by the Australian Government,” he said.

“The program is backed by a professional organisational structure within the Department of Defence, and both the Minister for Defence Industry and the Shadow Minister for Defence, among many others, have publicly supported the significant financial investment in submarine capability.

“While effective management of the program will continue to be important, Defence understands the need and the challenge to ensure there will not be a gap in Australia’s submarine capability during the transition from the Collins-class submarines to the future submarines,” he added.

“As for suggestions about different submarine designs, there is no ‘off-the-shelf’ design which meets Australia’s requirements and any modification of an existing submarine platform will, in itself, incur unacceptable risk.”

SIA’s statement comes in the wake of a new Insight Economics report which recommends buying a modified off-the-shelf design to replace Collins. The report was commissioned by electronics retailer and submarine blogger Gary Johnston, who runs the Submarines for Australia website.

Johnston says the report “…shows that Australia’s Future Submarine (FSM) project is extravagantly expensive, highly risky and, in an era of heightened tensions in the Asia Pacific, compromises the future defence of Australia.”

He adds that the project “…will cost far more than necessary and, because of its extended delivery schedule, will probably leave a very serious capability gap of several years when Australia may have no operational submarines at all.”

The report was contributed to in part by Australian National University Professor of Strategic Studies, Hugh White, and former Australian Public Service head Michael Keating.

“We will pay far too much for a boat that will do far too little,” Professor White said in an address to the National Press Club on September 27. “Our calculation in the report is that, in 2016 dollars, these 12 boats will cost us $40bn, plus $6bn for the combat system – well over $3bn a boat. In every major project like this, the costs escalate.”

In response, Defence Minister Senator Marise Payne has said the Insight Economics report was a “beat-up”.

“The consistent advice from Defence and actual experts in the field is that there are no military-off-the-shelf submarine options that meet Australia’s unique capability requirements,” she said.

“A ‘modified off-the-shelf’ submarine is an oxymoron.”