BROADCASTING, as you probably know, is a reserved matter. Sometimes, as when a young Paisley MP delivers a remarkable maiden Commons speech, BBC Scotland's broadcasting is less reserved than downright vacuous.

Mhairi Black might have electrified half the media-political world. Twitter might have been straining under an avalanche of praise from allies and opponents alike. Last week, Reporting Scotland was having none of that nonsense.

It was as though an editorial mute button had been pressed. In the absence of the old test card we got a reminder that applause in the chamber is frowned upon. That, supposedly, was the story, not Black's scintillating address. Everyone in the English-speaking world was out of step except BBC Scotland.

What's one little editorial slip? Nothing much. What, then, is a lengthening list of complaints directed at the BBC's content and coverage in changing political times? Just the oldest of rituals for battle-hardened Corporation executives adept at framing every assault as proof of journalistic virtue.

Nationalists allege bias before, during and since the referendum? The BBC has seen worse, week after week, election after election. Once it collided with Labour over Iraq, Dr David Kelly and dodgy dossiers. Now it has the Tories issuing threats, yet again, over everything from its programming to its website, its licence fee to – but of course – its impartiality.

In this game, as those executives will say with no little pride, the BBC can't win. That might be so. What's stranger is that invariably the Corporation's critics are also on a hiding to nothing. Who can prevail against that unique international reputation, all that vaunted public trust and affection, the reverence accorded to a national institution? Morally, the BBC has all the artillery.

Or so that story goes. Last week, however, another tale slipped into the public domain amid the fuss over Reporting Scotland's dismissive treatment of Black. Typically, we heard about it thanks to the BBC, an institution that often hands cudgels to its critics. The facts revealed should have troubled the Corporation's Caledonian branch more than any Tory minister. In reality, it was already well aware of the grisly truth.

To accompany its annual report and lofty thoughts from its trustees, the BBC produces a thing called the Purpose Remit Survey. Compiled by NatCen Social Research from online and face-to-face interviews, it is intended to inform the Corporation of public perceptions. The work is carried out in the autumn and published, as last week, in the following summer. Self-congratulation tends to ensue. This time, that could be awkward.

So who thinks the BBC is “good at representing my nation/region” in its network news and current affairs? In England and Northern Ireland, a very decent 61 per cent gave the thumbs-up. Some 55 per cent of people in Wales agreed. In Scotland, just 48 per cent of those surveyed thought their country was represented adequately across Britain by the British Broadcasting Corporation.

Perhaps the referendum ferment was to blame. Certainly the Audience Council Scotland, advising the trust, reported dismay over London's habit of dispatching correspondents and presenters northwards at the time of the plebiscite. There had been an “Anglified perspective” and undue focus on the official campaigns at the expense of “civic and community engagement”. The council also made remarks on “perceptions” concerning impartiality.

As criticisms go, it was all gentle stuff. No-one has ever explained why the BBC in London insists on sending staff to Scotland when BBC Scotland has journalists of its own. It was never obvious why James Naughtie should be seconded from Today to Good Morning Scotland for referendum duty. In any case, the Purpose Remit Survey was not telling the Corporation anything it didn't know.

Representing my nation? The Scottish figure last autumn might have been a miserable 48 per cent. Fully a year earlier, in 2013, when 60 per cent in England were pronouncing themselves satisfied, only 47 per cent of Scots were in agreement. If there was a referendum effect where attitudes towards the BBC were concerned, it began long before the vote. In that regard, previous versions of the Purpose Remit Survey are revealing.

In the autumn of 2013, for one example, 61 per cent in England and 65 per cent in Northern Ireland confirmed that the BBC was helping people to “understand politics in my region”. In Scotland, the figure was just 51%. What's more, that was a full 13 per cent drop since the winter of 2012-13. If you trust surveys and statistics even slightly, something fundamental was taking place in Scottish attitudes towards the BBC long before the referendum vote.

How could it be otherwise? If you voted Yes last year you might currently be experiencing the absence of surprise. It is no longer a secret that BBC Scotland has a problem with its audience and with its role. Similarly, you have to work hard to be astonished when you notice that in the autumn of 2013, 71 per cent of Londoners thought network news was doing a good job of representing their region. Just 57 per cent in the north of England felt the same. Still, 71 per cent against 47 per cent says a lot about Scotland and the BBC.

So why does the regulation of broadcasting remain, despite everything, a reserved matter? Those who were involved in the Yes campaign would regard the very question as simple-minded, but even within the limits of devolution the justifications are, shall we say, thin. Because the BBC is a cherished institution binding the country together (and all that)? The same is said of the NHS and it is fully-devolved.

Why, equally, is BBC Scotland still refused that often-debated “Scottish Six” bulletin? As John Nicholson, SNP MP for East Dunbartonshire and himself a former BBC man, put it last week, this is perhaps “the only country in the world” whose main evening news broadcast omits foreign coverage. The nightly Andy Murray bulletin takes in the odd exotic spot, of course, but the point stands: where Scotland is concerned, Westminster and the BBC take the same attitude. Never mind devolution: power reserved is truly power retained.

Presumably there are those who assume that BBC Scotland isn't up to the job of acting as a national broadcaster. If so, the Corporation would have to explain why that perception has been allowed to develop. As things stand, it has a job on its hands, you might have thought, dealing with the way it is already being perceived by its Scottish audience.

It fails – says a majority – to represent Scotland adequately across its network. Meanwhile, it fails 49 per cent of listeners and viewers who want to understand the politics of their own country better. And all of this has coincided with the independence argument and its aftermath. The Corporation is luckier than it realises to be under attack by the Tories.

If the (very) reserved BBC is failing Scotland, according to its Scottish audience, then the case for a different approach becomes unanswerable. A few more doses of River City will not put us all to sleep. Too many viewers and listeners have drawn their conclusions about trust, bias, representation and impartiality.

Dismissing them all as obsessed nationalists will not do BBC Scotland the slightest bit of good. It must be a terrible annoyance for executives, but broadcasters cannot pick their audiences.