The question everyone's asking about Barnaby Joyce.

Malcolm Turnbull will face community pressure over why Barnaby Joyce is not stepping aside from the ministry, former MP Tony Windsor says.

The deputy prime minister has been referred to the High Court to test whether his New Zealand citizenship by descent makes him ineligible to sit in parliament.

Mr Windsor, who previously held the seat of New England and was beaten by Mr Joyce at the 2016 election, said the community would soon question why his successor was not stepping aside from cabinet as his former ministerial colleague Matt Canavan did in similar circumstances last month.

Senator Canavan is also facing a High Court hearing over his Italian citizenship which was obtained by his mother without his knowledge.

“The question that will evolve very quickly is what’s the difference between (Mr Joyce) and others – there is no difference,” Mr Windsor told AAP on Monday.

“If he sits there, I think it’s a bigger problem for Turnbull.”

Attorney-General George Brandis told parliament, in answer to a Labor question, Senator Canavan had “decided that he would prefer to stand down” based on his “understanding of the facts”.

“The facts of Mr Joyce’s case … are much clearer to us than were the facts as known to Senator Canavan at the time he made his decision,” Senator Brandis said.

“On the basis of those known facts and clear solicitor-general advice, the government does not consider that there is sufficient reason for Mr Joyce to step down.”

He said there was “no compulsion” for Senator Canavan, who has also decided not to vote in parliament, to stand aside.

Mr Windsor said he would not rule out another tilt at Mr Joyce’s seat, mainly because he claims the Turnbull government had botched so many policies close to his heart: the national broadband network, climate, schools funding and water.

“I think Turnbull is terminal – you’ve only got to look at his face. He’s aged, he’s not enjoying it. I feel for him a bit,” Mr Windsor said.