Johnston's position "untenable": SA Libs

South Australian Liberal leader Steven Marshall says his federal colleague David Johnston should resign for disparaging Australian Submarine Corporation (ASC).

Mr Marshall described as "deplorable" comments by the defence minister that he wouldn't trust the government-owned enterprise to "build a canoe".

Senator Johnston on Wednesday said he regretted the "rhetorical flourish", which he said was aimed at ASC management rather than workers.

But Mr Marshall said he wasn't satisfied with the explanation.

"Unless he can rebuild some connection, some rapport, some confidence within the industry, then I don't think he has any alternative (but to resign)," he told reporters.

"I don't think that his current position is tenable unless he can rebuild that confidence with the sector."

SA Defence Industries Minister Martin Hamilton-Smith said the comment was a slap in the face to the thousands of hard working men and women who build and maintain Australia's naval fleet.