Defence Minister drowning over submarine sledge

Defence Minister David Johnston is tonight clinging onto his job, after he dismissed Australia's naval shipbuilders, saying he wouldn't trust them to build a canoe.

The Prime Minister is standing by his beleaguered frontbencher but smelling ministerial blood in the water, the Opposition went for the jugular.

Opposition leader Bill Shorten called on the prime minister to sack Senator Johnston.

Senator Penny Wong said the minister's position was "untenable".

After making the comment against the Government-owned, Adelaide based Australian Submarine Corporation, the Prime Minister disciplined him.

"Regrettably, in rhetorical flourish, I did express my frustrations in the past performance of Australian Submarine Corporation," Senator Johnston told the Senate.

"I regret that offence may have been taken."

The Opposition argued it was a long way short of an apology. 

South Australian Liberal Leader Steve Marshall even weighed in.

"I don't think his current psoition is tenable," Mr Marshall said.

Late today the Senate censured David Johnston, the highest parliamentary reprimand against a minister.