Christian Porter has resigned from Scott Morrison's ministry after revealing he had accepted an anonymous donation

Christian Porter has resigned from Prime Minster Scott Morrison's ministry

• Porter quits instead of pressuring trust to reveal donors.
• Energy Minister Angus Taylor will now temporarily take responsibility for Mr Porter's portfolios.

Christian Porter has resigned from Prime Minster Scott Morrison's ministry after revealing he had accepted an anonymous donation to help cover his personal legal fees.

Mr Porter's future on the frontbench had been in doubt following his declaration that a "blind trust" had paid for part of his discontinued defamation case against the ABC and journalist Louise Milligan.

Mr Morrison had offered no defence of his Industry and Science Minister and asked the head of his department, Phil Gaetjens, to investigate whether the declaration was in breach of the ministerial standards.

On Sunday, Mr Morrison said Mr Porter was unable to provide the necessary information and to "avoid any perception of conflicts of interest" had chosen to resign.

"He has this afternoon taken the appropriate course of action to uphold those standards by tendering his resignation as a minister this afternoon, and I have accepted his resignation," Mr Morrison said.

"His actions have been about upholding the standards.

"We believe they are incredibly important, and it is not just about actual conflicts, it's about the standards for ministers to have an obligation to avoid any perception of conflicts of interest that is ultimately what has led the Minister to make that decision this afternoon."

The Prime Minister revealed he was still waiting for the advice from Mr Gaetjens but given that Mr Porter has quit, "that matter is now concluded".

"There are grey areas in these issues, complex arrangements when applied to particular circumstances can be inconclusive," he said.

"But the Minister has taken the decision which errs on the side of upholding the highest standards."

Mr Porter will now move to the backbench — bringing to an end his six-year cabinet career — and Energy Minister Angus Taylor will temporarily takeover his portfolios.

In a lengthy statement, Mr Porter insisted his disclosure was within the rules but conceded the uncertainty over who contributed to the trust had become an "unhelpful distraction for the government".

"Ultimately, I decided that if I have to make a choice between seeking to pressure the trust to break individuals' confidentiality in order to remain in Cabinet, or alternatively forego my Cabinet position, there is only one choice I could, in all conscience, make," he said.

"Consequently, I provided the Prime Minister with my resignation earlier today.

"It is effective immediately."

Mr Porter updated his register of members' interests last Tuesday, revealing a blind trust known as the "Legal Services Trust" had made a "part contribution" to cover the costs of his lawsuit against the public broadcaster.

A spokesman for Mr Porter said he had "undertaken disclosure in accordance with the requirements of the Register and consistent with previous members' disclosure of circumstances where the costs of personal legal matters have been mitigated by contributions or reductions in fees".

"No taxpayers' funds were used in meeting the costs of the Minister's actions against the ABC and Milligan, which have now concluded," the spokesman said.

While Mr Porter insisted his declaration was within the rules, his decision to accept an undisclosed sum of money from an undisclosed source raised questions about his judgement.

Senator Birmingham conceded Mr Porter's disclosure was "an unusual one", and as such, the Prime Minister has sought precise and specific advice on that, as he's done in relation to previous questions around conduct and compliant.