Deputy Prime Minister Barnaby Joyce expects former federal minister Christian Porter to one day return to the frontbench, after he quit for failing to explain who helped fund his defamation case.

Mr Porter resigned after revealing he accepted mystery money through a “blind trust” for part of his legal action against the ABC over allegations of rape more than 30 years ago.

While the former industry minister does not think he has breached ministerial standards, he does not want to be “a very unhelpful distraction” for the coalition government.

• Related: Porter under pressure to reveal donors

Mr Joyce believes Mr Porter was right to resign.

“He has, like so many of us, gone to the corridor of the nearly dead,” M Joyce told the Seven Network on Monday.

“I bet you his electorate won’t resign from him though. He’s an incredibly astute politician, he’s incredibly capable.

“I’ll put money that we’ll see him back again.”

Employment Minister Stuart Robert defended Mr Porter as “an incredibly decent and smart operator”.

“He put a statement out yesterday, it’s heartbreaking reading when you look at what he’s been through,” Mr Robert told the Nine Network.

Mr Porter maintained the trustee had reassured him no money had come from lobbyists or prohibited foreign entities.

He did not want to “pressure” the trust for more information because that would make them “targets of the social media mob”.

“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,” Mr Porter said in a statement.

He launched defamation action against the ABC after it published a story about a now-deceased woman’s historical sexual assault allegation against Mr Porter.

The MP strenuously denied the claim and the case settled before trial.

Prime Minister Scott Morrison said Mr Porter took appropriate steps to uphold ministerial standards by resigning.

The opposition is vowing to pursue the former minister over the issue, including through parliament’s privileges committee.

Retiring Labor MP Joel Fitzgibbon labelled Mr Porter’s resignation inevitable.

“It closes another sad chapter in the prime minister’s slowness to act on these ministerial standards,” Mr Fitzgibbon told Seven News.

-AAP