Assistant Health Minister Fiona Nash has been censured in the Senate over conflict of interest claims, but Prime Minister Tony Abbott is continuing to stand by her.

Labor and the Greens claim Senator Nash has misled the Upper House several times in recent weeks over her former chief of staff's links to the confectionery industry.

The parties used their superior numbers in the Senate to interrupt Question Time and pass the motion. They now want Senator Nash to resign.

The censure motion has no legal consequences and the Government has dismissed it as a stunt.

Senator Nash came under fire for ordering the Health Department to take down its food rating website hours after it went live.

What is a censure? While ministers are neither appointed nor removed by the Senate, they are accountable to it. They are expected to account for their actions and policies by answering questions, providing documents and appearing before committees.

While ministers are neither appointed nor removed by the Senate, they are accountable to it. They are expected to account for their actions and policies by answering questions, providing documents and appearing before committees. Ministers have been censured for matters as varied as misleading the Senate, failing to answer questions on notice within the stipulated time limit, maladministration of a department and failing to declare an interest in a matter.

Ministers have been censured for matters as varied as misleading the Senate, failing to answer questions on notice within the stipulated time limit, maladministration of a department and failing to declare an interest in a matter. Although a resolution of the Senate censuring the government or a minister can have no direct constitutional or legal consequences, as an expression of the Senate's disapproval of the actions or policies of particular ministers, or of the government as a whole, censure resolutions may have a political impact.

Although a resolution of the Senate censuring the government or a minister can have no direct constitutional or legal consequences, as an expression of the Senate's disapproval of the actions or policies of particular ministers, or of the government as a whole, censure resolutions may have a political impact. For this reason they have frequently been moved and carried in the Senate. They provide a substitute to the usual inability, because of ministerial control, of the House of Representatives to discipline a minister.

Her former chief of staff resigned after it was revealed he had a shareholding in a firm that lobbied for junk food companies.

The Senate yesterday voted in favour of a motion asking Senator Nash to provide details of what measures were put in place to deal with any potential conflicts of interest, but she says providing that information would be a breach of privacy.

Senator Nash today argued against the censure motion.

"I can say to the Senate that every step of the way in this process, every step of the way, with every question that had been asked of me relating to this issue, I have acted in good faith, and I have provided to the Senate, and the Senate Estimates Committee, the facts," she said.

Speaking earlier in the Lower House, Mr Abbott stood by Senator Nash, saying: "Not a single person has done anything wrong in this case."

But Labor Senator John Faulkner says the public deserves to get answers.

"To treat questions in the Parliament and parliamentary committees with contempt is to treat the right of Australians to know how their government acts with contempt," Senator Faulkner said.

Labor Senator Penny Wong says the decision to move the censure motion was not taken lightly.

She says Senator Nash did not take appropriate steps to ensure her chief of staff's business past did not affect her policy decisions.

"This is a textbook example of a conflict of interest. Yet Senator Nash denies, and continues to deny, that there was anything untoward here," she said.

"So let me spell it out: the Assistant Health Minister makes decisions which directly affect the commercial interests and profits of companies in the food industry, and while she was making these decisions, her most senior adviser owned a lobbying firm which profited from helping food industry clients get what they wanted out of the Government."

The Leader of the Senate, Eric Abetz, vigorously defended Senator Nash.

"We on this side know Senator Nash to be a minister of integrity, a minister of capacity.

"She will continue to be a minister of integrity. She will continue to be a minister of capacity, committed to the service of the people of Australia," he said.