Mary Dejevsky: The Leveson Inquiry has switched its focus from the Murdoch press

Britain's culture secretary Jeremy Hunt leaves the High Court after giving evidence at the Leveson Inquiry (AP)

At the time, it must have seemed like such a good idea. With the country united in righteous indignation about the hacking of Milly Dowler's phone, and the gloss – that this was a criminal, nay heartless, act typical of a certain strand of the British press – the Prime Minister adopted a solemn mien and announced an inquiry.

But not only must it have seemed a good idea, in the sense of imposing the firm smack of government and simultaneously feeling the public's pain, it must have seemed copper-bottomed safe. An inquiry might not actually do any good, but what possible harm could be done by a three-part inquiry into "the culture, practices and ethics of the press"? Public money was earmarked; Lord Justice Leveson was appointed to preside, and the whole fandango swept into the Royal Courts of Justice with a speed quite extraordinary for anything initiated by government.

Less than 11 months on, David Cameron must be rueing the day he announced this inquiry. Nor will he be the first prime minister to be forced to reflect on the unintended consequences of rashly pandering to the public mood. Not only has the immediate trigger for the inquiry been partly discredited – that News of the World journalists deleted messages from the deceased Milly Dowler's voicemail, misleading her parents and the police into believing she was still alive – but the inquiry itself has come back to bite him. In a sure sign of regret, he is reported to be taking out his unhappiness on his chief civil servant, Sir Jeremy Heywood. Civil servants are like lawyers: they set out the options and recommendations, but you must take the decision and the blame.

With Leveson, it is too late. It is hard to pin down exactly when the balance tipped, but what began as an inquiry into the excesses of the press and how to curb them, has flipped almost unnoticed into a forensic expose of the symbiotic relationship between politicians and the media – and the politicians are coming off worse. So much worse that the Culture Secretary, Jeremy Hunt, in his evidence yesterday tried in vain to rekindle some indignation about phone-hacking. The truth was that he was on trial for his job, and, by extension, for his career.

In the circumstances, Hunt acquitted himself well, as indeed have many of the witnesses summoned to this inquiry, from Rebekah Brooks, the supposed fall-gal for the Murdoch media, to the procession of government ministers and advisers quizzed this week. One conclusion to be drawn is that money buys some pretty effective training in how not to come a cropper when the cameras are running and the questions keep coming: keep calm, submit a blizzard of documents, and carry on.

How damaged you think Hunt was by yesterday's encounter probably depends on what you thought before – which is a sign that, in six hours, he managed not to make the hole he was in much deeper. He did not conceal his largely sympathetic view of News Corp's bid for BSkyB. Nor would there have been much point in so doing, given the positive memo he had once sent Cameron on the subject. The question is whether, as a minister in a "quasi-judicial" role, he was able to separate his own views from the judgement he had to make for the Government.

Personally, I see no reason why a minister, including this minister, should not be able to separate the personal from the professional. One way or another, that is the nature of their job. The Business Secretary, Vince Cable, would have done the same, when the decision on the BSkyB bid rested with him. He may well, as he foolishly boasted to two reporters, have "declared war on Murdoch", but this would not necessarily have prevented him from observing the correct procedures and weighing his ministerial decision. The problem, as with Hunt, is that his private view became public. The problem for Cameron is that his instant response to Cable's indiscretion was remove him from the case; with Hunt, he seems not to have seen a similar danger.

The most sensible contribution to the BSkyB affair was made by the former Lord Chancellor, Lord Falconer, who said that such decisions should not rest with ministers, because that made them political. One of Hunt's points yesterday – repeated so often as to suggest it featured in his preparation – was that his decision to refer the BSkyB bid to Ofcom was unpopular with News Corp. Ergo, he implied, he was doing his "quasi-judicial" job.

Fairly or not, whatever awaits Hunt, the perception of bias in the BSkyB bid is likely to stick, even though he heeded legal advice, even though he referred the bid to the regulator, and even though, for quite other reasons, the bid came to nothing. And if his fate is sealed, the taint will extend to Cameron, for pushing what was always a contentious bid in his direction. Trying to distinguish between "sympathetic" and "supportive" to describe Hunt's approach, the hair- splitting attempted yesterday, will not really wash.

That the job of a favoured minister is at risk and the fall-out is approaching No 10 illustrates how completely the emphasis of the Leveson Inquiry has shifted. In the three weeks that relations between politicians and press have been under the microscope, it is the politicians' almost abject need for the press that has become apparent, far, far more than the press's need for the politicians.

In its scrutiny of that relationship in general, and the BSkyB bid in particular, Leveson is doing the sort of inquisitorial job of holding the executive to account that rightly belongs to Parliament. And if there is a lesson to be drawn from this unforeseen twist, it might be that modern Britain would benefit from the sort of separation of powers that many other democracies take for granted. Cross-party parliamentary committees are becoming more aggressive, but in a system that presupposes ministers are also MPs, the constitutional checks on their power are not good enough.