Defence Materiel Organisation chief executive officer Warren King's plea that Defence had learnt its lessons, lifted its game and was working hard to ensure history did not repeat has been rejected by experts who say they have heard it all before. Mr King had been asked to explain how, with depressing regularity, Defence pitches the acquisition of a new plane or boat or weapons system to government as a ''mature'' project only to have taxpayers called on to stump up millions of dollars - and even billions of dollars - for additional development further down the track.

One group of culprits was Defence industry salesmen who exaggerated the virtues - including the readiness - of their wares, he told the Foreign Affairs, Defence and Trade Committee. ''There was a time when marketeers from industry had more sway than they should have and we should have used the maxim 'trust and verify'.''

Over enthusiastic ''capability managers'' within Defence who wanted to acquire the latest technology - sometimes ready or not - were also in his sights. Mr King said the ''enthusiasm'' of such capability managers was now balanced against rigorous internal analysis of claims for a project's maturity. ''Now that's the sort of contestability I think we're getting better at.''

Andrew Davies, a senior analyst with the Australian Strategic Policy Institute who appeared before the committee on Tuesday, said Mr King's evidence echoed similar arguments by his predecessors.

''Time will tell if the claim they [Defence] are getting better is true,'' he said.

South Australian senator David Fawcett had asked Mr King how damaging ''conspiracies of optimism'' that often crept into major Defence buys could be countered.

Senator Fawcett was a former Lieutenant-Colonel in the Army with experience in the Defence Acquisition Organisation - a precursor to the DMO - before he went into politics.

Mr King said, ''I'd just like to start with a personal observation that a number of the projects you have referred to are quite old - I'm not excusing them, but they are old.

''We did too much trusting and not enough verification on some of those projects. I think we have moved on quite a distance from there.''

Neil James, the executive director of the Australia Defence Association, said the ''old project'' defence was not true in all cases.

''For years we have been being told that most of the projects that are in trouble are old ones from before the introduction of the first and second pass [approvals] system,'' he said. ''This excuse will progressively wear thin as time goes by.''

Mr Davies agreed: ''Many projects Senator Fawcett describes as suffering from 'a conspiracy of optimism' could more accurately be described as suffering from a failure of the systems engineering process that should underpin all complex acquisitions.''