The former minister defended his decision not to ask where the cash came from, claiming that doing so would expose his donors to “the social media mob” and that he was “not entitled” to know the source of the money.

But Labor is still demanding to know where the money came from and how much Porter received, claiming the situation was “absurd”.

“They contributed to a trust on the basis of confidentiality and a belief that their contribution would remain confidential within the rules of disclosure,” said Porter yesterday, in his first comments on the scandal that has claimed his position as Industry Minister.

“I am not prepared to seek to break the confidentiality of those people who contributed to my legal fees.”

Prime Minister Scott Morrison said that Porter’s resignation was “appropriate”.

“I expect my ministers, all of them, and myself, to uphold the ministerial standards and to act in accordance with those ministerial standards.”

Porter will now return to the backbench to serve as the member for the Western Australian seat of Pearce.

Opposition Leader Anthony Albanese said Porter still had many questions to answer as a member of parliament and was in breach of his obligations.

“He needs to answer where this money came from,” Albanese told reporters in Sydney.

“Members of parliament, as well as ministers, just can’t accept money from anonymous donors for a private legal matter. He is not fit to be a member of parliament.

-with AAP