The Government's response to revelations about the Culture Secretary's contacts with Rupert Murdoch's News Corp followed time-honoured precedent. The wagons were circled around the minister, and the special adviser was thrown to the wolves. Or, as expressed more brutally but not inaccurately by the veteran Labour MP Dennis Skinner to a tumultuous House of Commons yesterday: "When posh boys are in trouble, they sack the servants."

In this case, however, sacking the servants – or rather servant – is by a long way not enough. Not that the adviser, Adam Smith, did not know what was required of him. He said in his resignation letter that his activities had "at times" gone too far. He said that neither the content nor the extent of his contact with News Corp had been authorised by the Culture Secretary. And he spoke of an impression created that there was too close a relationship between the department and the company. The Prime Minister could not have done a better job of erasing his minister from the picture if he had dictated the letter himself. Everything was simply down to the overzealousness of a free-booting adviser.

The difficulty is that there is no such thing as a free-booting adviser. Indeed, there are actually provisions in place to ensure that political advisers fit into a formal chain of responsibility. The Ministerial Code is quite clear: so far as special advisers are concerned, the buck stops with the minister who appoints them, in this case with the Culture Secretary, Jeremy Hunt. They are not, and cannot be, independent, unaccountable operators.

Nor can Mr Hunt have it both ways, as he tried to in his Commons statement yesterday. If he knew what his adviser was up to in his almost daily communications with News Corp, he had to be departing from his obligation, in the BSkyB bid, to conduct an impartial, "quasi-judicial" process. But if he did not know what was going on – which is what he insisted and what his hapless special adviser also maintains – he was culpable, too. Either he was negligent in not keeping close enough tabs on a key member of his staff, or his judgement was flawed for appointing someone so untrustworthy in the first place.

None of the other points Mr Hunt marshalled in his defence yesterday cancel out this reality. He may indeed have involved independent regulators; he may indeed have cleared Mr Smith's involvement and its nature with his civil servants. But if privileged information was flowing from his department to News Corp, through whatever channel, and he was the minister in charge – as he was – it is he who bears the ultimate responsibility. The perception, if not the reality, is of partiality – in a bid which had the potential to transform the British media landscape – and perception in politics is all.

This is why, whatever submission Mr Hunt makes to the Leveson Inquiry and whenever he makes it, it is unlikely to reduce the impact of the email exchanges revealed this week. The Government in general, and the Culture Secretary in particular, could not but have been aware of what was at stake in News Corp's bid for BSkyB. Nor could they not have known how crucially important it was not only to be impartial, but to be seen to be so. Vince Cable's gaffe and subsequent loss of the BSkyB brief only underlined that. Mr Hunt erred – fatally – on the other side.