Under long-standing freedom of information laws, pending requests can be deleted once the minister leaves the role. But opponents have warned the law creates a loophole enabling scandal-plagued ministers to avoid scrutiny.

The Department of Industry, Science, Energy and Resources has begun deleting freedom-of-information requests relating to Mr Porter's "blind trust" saga on the grounds he is no longer the minister.

Mr Porter on Sunday resigned over revelations he received anonymous funding for his now discontinued defamation suit against the ABC and journalist Louise Milligan.

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Supporters of the ruling, made by the Information Commissioner, say responding to FOI requests is a time-consuming process, and the rulling allows public servants' time to be used more efficiently, rather than focusing on former ministers who often no longer had staff or an office.

But Mr Porter has stated he will recontest the seat of Pearce at the next election, despite questions lingering over the source of the funding. The former minister remains unable to explain where the money came from.

A spokesperson for shadow attorney-general Mark Dreyfus said Labor had no plans to change the law if elected.

But independent senator Rex Patrick, an advocate for government transparency, has revealed he will challenge the ruling in court and, if unsuccessful, move to amend the law in Parliament.

"People have a right to know how government is and was conducted. The idea that the resignation of a minister can somehow deny access by the public to matters which were being handled by that former minister is offensive," Senator Patrick said.

"This government has a culture of secrecy and wouldn't seek to remedy this anomaly in common law ... They'd be very comfortable with the current position in law."

Senator Patrick in August won a court battle to have freedom-of-information requests relating to the national cabinet made public.

He will challenge the decision relating to Porter, made via a common law ruling, in the Administrative Appeals Tribunal.

In a Senate inquiry submission on Monday, legal group the Grata Fund argued the law created a "significant gap" in public accountability, particularly given there had been 17 ministerial changes since the May 2019 election.

It claimed the public could only access vital information the outgoing minister chose to make public, or via the National Archives 20 to 30 years later.

"This decision leads to the absurd consequence that a minister can escape scrutiny simply by resigning or being shuffled around to a new position," it read.

"This approach creates a significant gap in accountability for acts of a sitting government. It is especially problematic given ministerial reshuffles are increasingly common in contemporary Australian politics."

Greens leader Adam Bandt said the loophole provided a "regular information-laundering opportunity" for the government.

"It's absolutely outrageous. A minister is resigning over a secrecy scandal, and the government is using that as an excuse to hide even more information. A minister resigning after receiving mystery donations should lead to more transparency, not less," he said.

"Scott Morrison must immediately close this loophole and ensure ministerial documents are transferred to new ministers when former ministers move on, especially if they leave under a cloud.

"If Scott Morrison won't insist on that practice, the law should be changed to stop the government using a transparency scandal as an excuse to become even more secretive."

One Nation senator Hanson said FOIs clearly related to a former minister's responsibility should be processed.

"But when it's about unrelated personal matters, as is the case with Mr Porter, it's inefficient and unnecessary to process such requests," she said.

"If Senator Patrick continues to pursue Mr Porter in the Senate, he will not have my support."

Senator Hanson claimed the money Mr Porter received did not consitute campaign funds, and said she was "very disappointed" the Prime Minister accepted his resignation.

"This was not vote-buying. It was a few people supporting Mr Porter in a personal defamation case," she said.

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