It was not until three years later that Julia Gillard asked Thomson to leave the Labor caucus. The presumption of innocence is a tenet of law, not a tenet of the law of politics. In those three years the Labor government and Labor Party suffered serious damage to their credibility. The trade unions fell into disrepute. The government lost power. The new government has set up a royal commission into union corruption. The Thomson case was not the chief reason for Labor's woes, of course, but an important one. And the reputation of politicians everywhere sank even deeper into the mire of public disgust. The essence was that a political party tolerated the intolerable because of tribal loyalty. Precisely this syndrome is on display in the Abbott government. The details are completely different, but the government's handling of Assistant Health Minister Fiona Nash and her chief of staff reveal the same mindset.

Nash has not defrauded anyone of money. She is not accused of a crime. But consider this series of outrages exposed by Fairfax Media's Amy Corderoy in the past fortnight. Nash is the minister responsible for food policy and alcohol policy in the federal government. She knowingly employed a former lobbyist for the food, beverages and alcohol industry as her chief of staff. His name is Alastair Furnival. He kept a half-interest in his lobbying firm while working for the minister. The other half was owned by his wife. The firm's clients include the owner of the Cadbury and Kraft businesses. They also include the Australian Beverages Council, representing the $7 billion-a-year soft drink industry. And the firm has done work for the alcohol industry at least as recently as 2012.

The minister evidently gave Furnival power over policy decisions. He made a series of decisions that favoured his firm's clients at the expense of public health interests. He overrode Health Department objections and deleted a government website on a new rating system for healthy food on the day it went public. The ''health star rating'' system had been two years in the works, developed jointly with state governments. The public servant who had objected was transferred six days later. Furnival stripped the federal funding from a key public health advocacy group on drugs and alcohol, the Alcohol and Other Drugs Council of Australia.

The council has supported the idea of taxing alcohol by volume, and other policies opposed by the alcohol industry. Furnival told the group at a meeting in December that they were to be lose their funding. One of the council's directors, the GP and former Liberal MP Mal Washer, said: ''There was no reason given [by Furnival] for the cut except for 'we don't have enough money and have a nice day', but, well, it's amazing what they can find money for.'' Washer said he contacted Nash's office several times, but had only been able to speak with Furnival. ''Normally when you contact them, they will have a yarn with an ex-federal colleague,'' he said. The head of the Australian Medical Association, Steve Hambleton, said : ''When we see adverse effects and acute side-effects from a toxic product continuing to rise we have to really question the wisdom of defunding a body that is trying to reverse that.'' Nash shut out other public health groups that asked to speak to the minister; they were directed to deal solely with Furnival.

At a key meeting with state governments on food policy in December, Nash and Furnival attended to represent the federal government. Neither disclosed Furnival's conflict of interest. And when opposition senators asked Nash about the Fairfax reports of the conflict of interest, she misled the Parliament. ''My chief of staff has no connection with the food industry and is simply doing his job,'' Nash told the Senate on February 11. Referring to Furnival's lobbying firm, she said: ''There is no connection, whatsoever, between my chief of staff and the company Australian Public Affairs''. She returned to the chamber eight hours later and corrected the record. Four days later Furnival resigned. In the course of all this, two of the Abbott government's ethics codes had been breached. Furnival broke the ministerial staff standards that require staff to ''disclose, and take reasonable steps to avoid, any conflicts of interest (real or apparent) in connection with their employment.'' He also broke the rule that staff ''divest themselves, or relinquish control, of interests in any private company or business and/or direct interest in any public company involved in the area of their ministers' portfolio responsibilities.'' More seriously, Nash broke the Abbott government's Statement of Ministerial Standards, which demands good decision making and ''in particular, ministers are required to ensure that official decisions made by them as ministers are unaffected by bias or irrelevant consideration, such as considerations of private advantage or disadvantage.'' If there were a federal version of NSW's Independent Commission Against Corruption, Nash and Furnival would be under investigation for corrupt behaviour.

The ICAC Act defines corrupt conduct as ''any conduct of any person (whether or not a public official) that adversely affects, or that could adversely affect, either directly or indirectly, the honest or impartial exercise of official functions by any public official, any group or body of public officials or any public authority, or ''(b) Any conduct of a public official that constitutes or involves the dishonest or partial exercise of any of his or her official functions, or ''(c) Any conduct of a public official or former public official that constitutes or involves a breach of public trust.'' At core, Nash as minister has presided over structural corruption. Not personal venality, but structural corruption. She handed federal power to the food and beverage and alcohol industry. Not in a figurative sense; she allowed an industry lobbyist to run policy. She is the Assistant Minister for Health but behaved like the minister for big sugar and big alcohol. Prime Minister Tony Abbott's reaction?

He has scapegoated Furnival and protected Nash. He is trying to tough it out. His spokeswoman said the prime minister ''has confidence in Senator Nash'', and ''with the staff member now departed, the matter has concluded''. Even if Nash did not personally make the decisions to pervert public policy in favour of corporate interests, she is at the very least guilty of serious misjudgement. Abbott has decided he cannot afford to lose a minster so early. In reality, he cannot afford to keep her. This week Nash's senior minister, Health Minister Peter Dutton, prepared Australia for a major reform of Medicare. He began: ''Today I ask you to help steer our country to a frank, fearless and far-reaching discussion on our health system. Why? Well, partly the answer lies in the latest statistics on obesity and diabetes in this country.'' Here he immediately confronted a credibility problem. Thanks to the antics of Nash and Furnival, he could not be taken seriously when he continued: ''Rising rates of obesity and diabetes may be the seeds of a future crisis - yet they are just two of several that we as a nation and society must confront.'' The government must to address the sustainability of Medicare. But it will require public trust. Tolerating Nash's conduct is the wrong way to build it. Labor and the Greens will pursue the matter in Senate estimates committees.

Abbott should recall his reprimand to Gillard for protecting Thomson: ''If the prime minister had any real ticker she would have made it crystal clear that this is absolutely unacceptable conduct and she wouldn't have been running around the countryside saying that she has full confidence in the Member for Dobell [Thomson] because if she has full confidence in that member, she presumably thinks that there's nothing untoward in what seems to have been done and I don't think that's a tenable position.'' Abbott was right then. He needs to apply the same standard. He cannot tolerate the intolerable out of tribal loyalty. Before taking the prime ministership, Abbott said: ''The point of being prime minister is that you've got to be a national leader, not just a tribal chief.'' Loading The Nash scandal is a test of whether he's capable of just that. Peter Hartcher is the political editor.