Opposition Leader Anthony Albanese says Barnaby Joyce has learnt nothing from his mistakes after he backed Christian Porter to make a future political comeback.
Mr Porter resigned as industry minister on Sunday after revealing some of his legal fees for his defamation case against the ABC were paid through a blind trust.
Mr Joyce believes Mr Porter deserves a second chance to serve as a minister at a later point.
But Mr Albanese said the acting prime minister's comments showed a lack of judgement.
"Barnaby Joyce just shows that, once again, a reminder that he has no integrity, that he's someone who shouldn't be in a position of being acting prime minister," he told reporters in Sydney on Tuesday.
"If this is his attitude, he has learnt nothing from his own mistakes."
Mr Joyce spent more than three years on the backbench after he resigned as deputy prime minister over a sexual harassment allegation he strenuously denied.
The claim came after revelations of his affair with a former staffer who is now his partner.
He returned as Nationals leader in June after defeating Michael McCormack.
The acting prime minister described Mr Porter's decision to accept the anonymous donation as "not a good day at the wicket".
"My own recommendation is that he is an incredibly capable politician," he told reporters on Monday.
Mr Joyce said the WA MP should be given another chance at a senior role in the future if he used his time on the backbench effectively.
Mr Porter sued the national broadcaster over a story about a historical rape allegation he strongly denies.
Mr Albanese said it was wrong for him to "pretend" he didn't know where the money came from.
"It's wrong to continue to sit in the parliament and deflect blame for what is Christian Porter's own actions in taking legal action against the ABC," he said.
"This is a clear breach of pecuniary guidelines"
He said the government would be rendered irrelevant if more action was not taken.
"That's why Christian Porter's position is simply untenable."
Australian Associated Press
