Federal Labor is demanding an independent inquiry into whether Employment Minister Michaelia Cash breached ministerial standards and tried to keep allegations against the former head of the construction watchdog quiet from Cabinet.

Key points: Cash knew of allegations Hadgkiss breached Fair Work Act

Cash knew of allegations Hadgkiss breached Fair Work Act Cash did not notify Cabinet of breach when Hadgkiss was appointed ABCC commissioner

Cash did not notify Cabinet of breach when Hadgkiss was appointed ABCC commissioner Turnbull says Hadgkiss' appointment to ABCC was act of Parliament

Turnbull says Hadgkiss' appointment to ABCC was act of Parliament Shadow employment minister says legislation would need Cabinet approval

Nigel Hadgkiss resigned as commissioner of the Australian Building and Construction Commission (ABCC) last week, after admitting he broke Fair Work Act laws between January 2014 and July 2016.

In the Federal Court, Mr Hadgkiss admitted he knew about material distributed by the precursor to the ABCC, the Fair Work Building and Construction Commission (FWBC), that suggested employers could make reasonable requests to stop union officials holding meetings in workplaces.

Under changes to the laws, the employer no longer had that right and unions could meet workers in meal rooms for talks if needed.

Mr Hadgkiss was the head of the FWBC at the time.

Last week, Senator Cash told Parliament she had been made aware of the allegations In October 2016 — but Mr Hadgkiss was appointed commissioner of the ABCC in December 2016.

Shadow employment minister Brendan O'Connor argued the resignation of Mr Hadgkiss should not mean the search for accountability ends.

"Of course the Government doesn't have a loyalty gene, of course they were going to immediately throw Mr Hadgkiss under the bus," Mr O'Connor told ABC RN.

"But this is about whether in fact the Minister should have reported this matter, disclosed this matter to Cabinet."

The allegations by the Construction, Forestry, Mining and Energy Union (CFMEU), prompted Senator Cash to defend her handling of the matter.

She said it would be wrong for the Government to stand down a government official every time the CFMEU made an accusation against them — suggesting the union had a reputation for being litigious.

"The litigation that is referred to was public knowledge, so that's the first point," Prime Minister Malcolm Turnbull told reporters.

"Secondly, it obviously had to take its course.

"Thirdly, Mr Hadgkiss became the ABCC commissioner by virtue of an act of Parliament, because he was already the commissioner of the Fair Work Building Commission, which then became transformed into the Australian Building and Construction Commission, and given obviously stronger powers and the ability to levy greater fines."

But Mr O'Connor argued that legislation would have had to be signed off by Cabinet, which was either not told about the allegations by Senator Cash or ignored them.

"If Cabinet made a decision about the transitional provisions without being provided information about the allegations against Mr Hadgkiss, yes, then I believe there is a ministerial breach here," Mr O'Connor said.

"We've asked the Prime Minister to examine this independently and come back with the answers."