THE Collins Class submarine fleet is among the world's worst, a new assessment says, but a later retirement date for the troubled fleet is possible with improved upkeep.
Part two of the Coles inquiry into the submarines, which have been plagued by maintenance problems, concluded they were available for operations for barely half the time of comparable countries' navies.
''It's quite clear from Coles's report that we fall substantially below any comparable international benchmark,'' Defence Minister Stephen Smith said of the report on Wednesday.
But a separate study of the service life of the Collins Class found there was no technical reason why the six submarines should not reach their expected retirement dates between 2024 and 2031 and could be kept in service a further seven years.
This could plug the feared capability gap, where Australia was facing having too few submarines between the retirement of the Collins and the commission of a new fleet. The government aims to decide next year whether the successor fleet of 12 submarines will be Australian-built or foreign-bought.
But the inquiry, led by British expert John Coles, found that the Navy had not given clear, unclassified explanations as to what it wanted the Collins Class to achieve operationally and said there was a ''clear lack of a performance-based culture'' in the Collins Class Sustainment Program.
The report also identified ''unclear lines of responsibility'' and ''poor planning''. And it cited poor information flow that meant the program was ''not in a position … to make optimised long-term decisions''.
The Navy had made improvements but not enough to fix all of the problems, it concluded.
But Coalition defence spokesman David Johnston said the government still needed to fix the problems before talking about having closed the capability gap.
''Labor announced 12 new submarines in the 2009 white paper but since then have done nothing except rip money from the defence budget, and these submarines simply do not materialise overnight,'' he said.