The scandals that have plagued Lord Goldsmith point to a constitutional mismatch at the heart of the attorney general's role

There are two kinds of scandal that can befall Britain's attorney generals. The first involves an act by the individual office-holder. Revelations about the immigration status of Baroness Scotland's housekeeper fell into this category, prompting predictable calls for her head to roll. The fact that Scotland had herself played a role in legislation designed to crack down on employers whose predicaments were, incidentally, just like hers, was an aggravating factor.

Then there are events that resemble a hurricane more than a storm, and lead all the way to calls for the abolition of the office itself. Scotland may be remembered as the first female and minority attorney general in the office's 700-year history, but in this respect she remains utterly eclipsed by her predecessor, Lord Goldsmith.

Goldsmith presided over no fewer than three incidents that could be filed under the category of imperilling the very office of attorney general. His advice over the legality of the Iraq war has provoked scrutiny for almost seven years now. Yesterday's call by Lord Steyn, a former law lord, for a decisive ruling on the issue added to an already impressive list of judicial and political opinion that questions remain to be answered ? principal among them being was Goldsmith "leant on" by Tony Blair to change his advice.

Such is the gravity of the question that it's easy to forget the other major controversies of Goldsmith's tenure. In 2008 he was accused of unacceptably intervening in a decision to drop a fraud investigation into arms manufacturer BAE Systems following threats from Saudi Arabia ? a case described by the council of Europe earlier this year as "the most prominent example of suspected political interference in the criminal justice system in recent years".

And then there was cash for honours. Goldsmith was widely attacked during the scandal for intervening in decisions over whether Blair and others should be charged, despite the obvious potential for conflict of interest, given his close relationship with the prime minister and status as a member of the government.

Of course Goldsmith, who is more than capable of mounting persuasive submissions in his defence, can draw attention to controversies surrounding numerous previous attorney generals, arguing that sensitive decisions are part of the job. In some cases, history ? if not constitutional law ? remembers such interventions fondly. Take the decision by the 1920s Labour attorney general, Sir Patrick Hastings, to stop the prosecution for sedition of a Communist trade unionist, or 1970s Attorney General Sam Silkin's refusal to prosecute Post Office workers in 1977 for their boycott of apartheid South Africa.

Whether history will be kind to Goldsmith remains to be seen. His actions as attorney general may already have had long-term consequences by exposing the fundamental unsustainability of the role in ways constitutional experts could previously only have theorised about.

In many ways the problem is as simple as this: the job description just does not work. The attorney general is tasked with the provision of independent advice to the government as its chief legal adviser, alongside the political duties of being a member of the government, with superintendence of the prosecuting authorities thrown in for good measure. It is a combination so conceptually challenging that even the office-holders struggle with it.

When asked whether he was "actually a politician", Lord Goldsmith has responded: "I am not sure about that, actually." If that seems basic, try asking whether the attorney general is a member of the cabinet. "The attorney general is not a member of the cabinet but may attend when his or her responsibilities are on the agenda," states a formal protocol published in July. So the attorney general should not attend cabinet routinely? Wait: "The prime minister has confirmed that Baroness Scotland is to continue to attend cabinet on a regular basis," a statement put out by Scotland's office says. Hardly a shining example of constitutional certainty.

It gets more tangled still. This maybe-politician-cum-maybe-cabinet-member maintains a role in decisions about whether to prosecute in individual cases. Recent reforms mean that this only applies in "exceptional cases" ? for instance where national security is concerned. That is, in the cases where the most is at stake and the perception of independence is most important.

"The public no longer believes in or accepts these constitutional symbols or fantasies," wrote legal scholar Graham Zellick in 1985 ? but the words are as true as ever today. "The simple fact remains that the law enforcement decisions are taken by a political figure, a member of the government who owes his office to the prime minister and may well be looking in that direction for political or judicial advancement."

This is not a question of individual attorney generals acting properly or not. When it comes to conflicts of interest, the established legal test is whether a "fair-minded and informed observer, having considered the facts, would conclude that there was a real possibility" of bias. I'd be surprised to find any such observer who would regard the current constitutional role of the attorney general as sustainable