At the core of the problem is the application (or non-application) of the important principle in constitutional and administrative law delegatus non potest delegare, which means that "no delegated powers can be further delegated." The largely unregulated role of ministerial advisers, exercising executive power in the name of the minister, remains problematic - and there is little, if any, inclination to address it.

The grey and undefined area of authority in which advisers operate raises complex issues relating to both influence and accountability.

Even if they do not direct public servants, the absence of any explicit code of conduct can, and often does, mean a lack of clarity which, in turn, can lead to disputes over the proper role of ministerial staff and the responsibility and accountability of the minister for their actions when controversy arises. It places unfair pressure on sometimes very junior officials, especially when done via telephone with no protective paper trail.

The latest setback to any meaningful reform comes with Prime Minister Scott Morrison's rejection of a recommendation in the Thodey review of the Australian Public Service calling for ministerial staff to be subject to a formal, legislated code of conduct.

The review, chaired by businessman David Thodey, and set up by former prime minister Malcolm Turnbull, found the number of ministerial advisers had jumped 32 per cent since 2000 and effectively constituted a new layer of government.

While acknowledging that ministerial advisers are currently expected to abide by a statement setting out standards of behaviour, the review found there was no formal induction process and little training, and said there was a need for code of conduct with "effective mechanisms for accountability and compliance".

The government's rejection of the recommendation elicited a collective cry of dismay from the public service, and the Public Service Commissioner Peter Woolcott was merely the latest in a long line of public service chiefs to have grappled with the issue and its implications for the service as a whole.

In a speech last month, Mr Woolcott called for ministerial advisers to be given clearer instruction on their role and how they relate to the public service. Ministerial staff and public servants needed to better understand each other's roles and learn how to work more effectively together.

"There is a strong need to improve and roll out better training and guidance for APS employees and ministerial staff in their respective roles," Mr Woolcott said.

The wider issue, however, concerns not just the operation of the public service but the democratic process itself. Political and administrative accountability are key planks in any democratic system, and to seek to blur or obfuscate the lines of accountability is to damage and diminish that process.

The exercise of "plausible deniability" has now become part of the ministerial lexicon in Australia, and it represents a corruption of the democratic process.

Over the years, under both Labor and Coalition governments, there have been multiple examples of staffers exercising forms of executive delegation in the names of their ministers by instructing public servants while the government itself imposes a barrier to their scrutiny by Parliament.

Ministers have consistently resisted moves to have their staff either appear or answer questions at parliamentary committees. The practice has become known as the McMullan principle, named for a former Labor minister in the Keating government, Bob McMullan, who ordered his staff not to give evidence to a parliamentary committee, arguing that "ministerial staff are accountable to the minister and the minister is accountable to the Parliament and, ultimately, the electors".

The infamous Children Overboard incident in 2001, in which staffers played a key role but were protected from questioning by parliamentary committees, was a prime case in point. Indeed, the then Public Service Commissioner, Andrew Podger, noted in his own evidence that there was "a case for some articulation of the values and code of conduct of ministerial officers".

The report of the Senate inquiry into the incident noted "a serious accountability vacuum at the level of ministers' offices arising from the change in roles and responsibilities, and the kinds of intervention engaged in by ministerial advisers".

In countries with a political system similar to Australia, attempts to resolve the issue have had mixed success. In Canada, the passing in 2006 of the Federal Accountability Act enshrined in legislation many of the former guidelines; it also brought ministerial advisers into the category of public office holders and subject to the scrutiny of the Conflict of Interest and Ethics Commissioner.

However, in the United Kingdom, a flurry of reform that was initiated by prime minister Gordon Brown when he succeeded Tony Blair in 2007 has had little apparent success.

When Blair was elected in 1997, he promulgated an executive order that enabled unelected political appointees - in this case, prime ministerial staffers - to instruct civil servants. The order in council formally empowered Jonathan Powell, his chief of staff, and Alastair Campbell, his press spokesman, to give orders to officials.

It was, to say the least, a controversial move. While the formal delegation of ministerial authority is easily justified in terms of managerial efficiency and streamlined administration, such a defence ignores the affront to principles of ministerial accountability and the Westminster system that such empowerment of unelected, and unaccountable, individuals inevitably entails. As critics at the time noted, it represents a corruption of the executive, the parliament and the civil service.

The unprecedented delegation power, as deployed, was to have serious consequences for the integrity of British government.

One of those so empowered, Alastair Campbell, became, in the words of political commentator Peter Oborne, "the most powerful figure in Downing Street besides the prime minister".

Oborne wrote in his book The Rise of Political Lying: "He was able to order most cabinet ministers - Chancellor Gordon Brown was an exception - around more or less as he liked, and exert enormous power throughout Whitehall. In due course, in a frightening abuse, he was even allowed to chair meetings with intelligence personnel present."

Campbell's public prominence was further heightened through his efforts to make a case for Britain's commitment to military action in Iraq. He was accused, inaccurately if not falsely as it turned out, of pressing the intelligence community to "sex up" its dossier on Iraq's weapons program.

The suicide of whistleblower David Kelly, a government scientist, over the affair prompted Campbell's departure from Downing Street, and led to the government setting up an inquiry chaired by Lord Hutton. Hutton found that Campbell had impressed upon the chairman of the government's Joint Intelligence Committee, John Scarlett, "that nothing should be stated in the dossier with which the intelligence community were not entirely happy".

But Lord Hutton nevertheless expressed concern about the influence Campbell exercised when he made it clear to Scarlett, on behalf of the prime minister, that 10 Downing Street wanted the dossier to be worded to make as strong a case as possible in relation to the threat posed by Saddam Hussein's alleged weapons of mass destruction.

Brown's very first act as prime minister was to revoke Blair's order in council. In a Green Paper, Brown and his secretary of state for justice, Jack Straw, urged a clarification of "the legitimate and constructive role" of special advisers and deemed it "inappropriate" that they be invested with delegated powers.

Events of recent weeks suggest such concerns no longer apply. New Conservative prime minister Boris Johnson's chief adviser, Dominic Cummings, has emerged even more powerful than Tony Blair's Alastair Campbell.

The Chancellor of the Exchequer, Sajid Javid, quit rather than be told he had to sack his aides and submit to Cummings taking control of financial policy via a joint team of advisers. Johnson stood by his adviser in what the Financial Times called "an astonishing decision; a chaotic, unnecessary and damaging outcome for the government".