Prime Minister Scott Morrison has ordered an investigation amid allegations former ministers Christopher Pyne and Julie Bishop might have breached parliamentary rules.

Key points: Scott Morrison orders a review into the post-political careers of all ministers

Scott Morrison orders a review into the post-political careers of all ministers Christopher Pyne and Julie Bishop have faced criticism for the jobs they have taken since leaving politics

Christopher Pyne and Julie Bishop have faced criticism for the jobs they have taken since leaving politics The Statement of Ministerial Standards dictates former ministers cannot lobby in their former portfolio for 18 months

The former defence and foreign affairs ministers have attracted criticism from Labor and the crossbench after accepting roles with consulting firms since quitting politics.

They deny they have breached the Statement of Ministerial Standards, which states former ministers cannot take lobbying jobs for 18 months after leaving office.

The Government's Senate leader, Mathias Cormann, told Parliament Mr Morrison had written to the secretary of his department to investigate whether Mr Pyne and Ms Bishop had broken the rules.

He said the careers of all former ministers, from both the Coalition and Labor, would be assessed.

"As part of this, [Mr Morrison] has sought advice on actions that can be taken to ensure compliance with the code," Senator Cormann said.

"Additionally, as part of this advice, [Mr Morrison] has asked the secretary about the application of the provisions of the Foreign Influence Transparency Scheme Act 2019 to the activities of former ministers and elected representatives."

Senator Cormann announced the review as Centre Alliance sought to refer Mr Pyne's post-political appointment to a Senate committee for an inquiry.

But following Senator Cormann's announcement, senator Rex Patrick deferred calling for that inquiry until a later date.

"Minister Cormann will inform the chamber of the response. I will wait to see what the response is," Mr Patrick said.

"If I am not satisfied, I will press for the inquiry to proceed.

"This is a very important issue."

Ms Bishop was the foreign affairs minister who overhauled the Government's approach to foreign aid spending. She is now working for one of the biggest beneficiaries of that policy.

On Tuesday, Labor's Penny Wong said Ms Bishop's new job with private aid contractor Palladium was a breach of ministerial standards.

Senator Patrick has repeatedly called on Mr Morrison to intervene following Mr Pyne taking a job as a defence consultant with multinational business advisers EY.

Mr Pyne was the defence minister until the May 18 federal election.

Ms Bishop stepped down as foreign minister after the Liberal leadership spill ended her tenure as the Liberal Party's deputy leader.