An investigation by the head of the Prime Minister's department has found former ministers Christopher Pyne and Julie Bishop have not breached ministerial standards by taking up new jobs.

Key points: Christopher Pyne took a defence consulting role after finishing as defence minister, and former foreign minister Julie Bishop joined a foreign aid company

Christopher Pyne took a defence consulting role after finishing as defence minister, and former foreign minister Julie Bishop joined a foreign aid company An investigation by the head of the Prime Minister's department has found they haven't breached the ministerial standards

An investigation by the head of the Prime Minister's department has found they haven't breached the ministerial standards The standards ban former ministers benefitting from their previous roles for 18 months

Former defence minister Mr Pyne was hired as a defence consultant by business advisers EY, as the firm seeks to expand its expertise in the defence industry.

Ms Bishop, who served as Australia's first female foreign minister, has joined the board of Palladium, which manages hundreds of millions of dollars in contracts from the Department of Foreign Affairs and Trade.

The pair had faced criticism they were using unique knowledge gained during their time in the ministry to benefit in the private sector, and Labor demanded Prime Minister Scott Morrison intervene.

The Statement of Ministerial Standards bans former ministers from taking "personal advantage of information to which they have had access as a minister, where that information is not generally available to the public".

An investigation was launched by Department of Prime Minister and Cabinet secretary Martin Parkinson.

"What is important is that whatever employment they take on does not put them in breach of the Statement of Ministerial Standards," Finance Minister Mathias Cormann told the ABC's AM program.

"And the advice that the Prime Minister has received from the secretary of his department independently is that former ministers Pyne and Bishop are not in breach."

"Dr Parkinson reviewed all of the relevant information, he spoke to both former ministers Pyne and Bishop, and his advice to the Prime Minister is there's no breach of ministerial standards — and that is the advice that I will be providing to the Senate this morning."

The Federal Opposition drew attention to Mr Pyne and Ms Bishop's long tenure in parliament and the ministry, saying it did not "pass the pub test".

"How on earth can Australians believe that Mr Pyne or Ms Julie Bishop, until recently the Minister for Foreign Affairs, were not already preparing for their post-politics careers while serving out their final days in their ministerial offices," Labor frontbencher Kristina Keneally told the Senate.

"This is not something just 'inside the Canberra bubble' Mr Morrison, these are ethical standards."

Crossbench and Opposition launch Senate investigation

Senate crossbencher Rex Patrick had threatened to establish a Senate inquiry into the ministerial standards, but said he would wait to see the result of Mr Parkinson's investigation.

The South Australian said he would attempt to establish an inquiry after the Parkinson investigation, suggesting it may even attempt to call the Prime Minister and Dr Parkinson to give evidence.

"We almost certainly will need to invite Mr Pyne, such that his side of the story can be told ... we'll have to probably talk to Ms Bishop as well.

"They're familiar with the building, they'll know where the committee rooms are."

Senator Patrick's motion was successful, with Labor backing the move.

One Nation leader Pauline Hanson said it was time to look at whether the ministerial standards needed to be changed.

"I have a grave concern about people who have held ministerial positions, dealt with companies who have received a million dollars, if not hundreds of millions of dollars in contracts, and [are] now working for those firms," she said.

"It doesn't look good."

Former deputy prime minister Barnaby Joyce said he would read the findings of Dr Parkinson's report, but he did not seem convinced the public would be satisfied.

"It passed the investigatory test, but obviously I think that people rightly have questions that they want answered," the Nationals MP said.