Mr Smith said last night the submarines were a vital part of the country's maritime national security capability.
"But problems with the availability of the Collins-class are longstanding, deeply entrenched and well known to the public," he told the Australian Strategic Policy Institute.
He said the problems were significant and technically complex, and they had to be sorted out before work could begin on plans for 12 replacement "future submarines" promised in the Rudd government's 2007 defence white paper.
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