Malcolm Turnbull has accused Labor leader Bill Shorten of being an apologist for the union "heavies" he relies on for his leadership.
The prime minister launched his unprompted attack part way through taking questions from journalists on the government's new initiative to put lifetime bans on asylum seekers who try to come to Australia by boat.
"Yesterday, we saw Bill Shorten apologise for the unions, to defend the unions and condemn the coalition's efforts to restore the rule of law to the construction sector," he told reporters in Sydney on Sunday.
"He was there at the Labor state conference in Queensland playing up to the CFMEU, and all of the union heavies upon whom he relies for his leadership."
Mr Shorten did attack the government for wanting to keep Family First senator Bob Day in the Senate just long enough to secure one more vote in "their attack on unions".
Senator Day - a keen supporter of the government's industry relation bills before the Senate - announced two weeks ago he was resigning from parliament to deal with his collapsed building company.
Since then his position has been less clear amid suggestions of him finding an unnamed investor to save the company.
"This phantom investor to which he refers, nobody knows," Labor's industrial relations spokesman Brendan O'Connor told Sky News.
"He has to explain whether indeed there is a real investor. That should be disclosed publicly,"
Labor also wants the government to explain whether it has been talking to Senator Day to delay his resignation.
"We have watched the gun for votes scandal, we wonder whether in fact they have been talking to Senator Day and I think they need to come clean on that."
Mr O'Connor was also quizzed on Labor's standing on including domestic violence leave being included in industrial awards.
He said Labor made a commitment to a five-day statuary minimum. The ACTU is pursuing 10 days.
He commended companies like National Australia Bank that have included domestic violence leave into their agreements.
Mr O'Connor did not believe the inclusion of a domestic violence leave provision would be misused.
"Victims of domestic violence are less likely to use such a provision because of the continued stigma associated with being a victim," he said.
The ABC, the public broadcaster, has just concluded its agreement and has been criticised by the government for being too generous.
The three-year deal includes a two per cent increase and a domestic violence leave provision, which Mr O'Connor thought "quite acceptable".
"If you measure it against any agreement in the public and private sectors, you would have to say it was within that realm," he said.
