"A choice of two futures" is how the Yes campaign characterise the decision Scottish voters face on Thursday 18 September. Either stick with one of the most unequal countries in the western world, ruled by governments you didn't even vote for, or take control of your own future. No middle options.

But it's also a slogan that could just as easily have been applied to the BBC's dilemma as it neared the closing stages of this campaign. You see, there are different components of the corporation's self-image that suddenly became utterly incompatible with each other in the context of a Scottish independence referendum.

On the one hand, there is the unspoken mission to foster British unity and a sense of pride in being British, as betrayed by countless programme titles along the lines of The Great British Bake Off. On the other hand, there is the BBC's global reputation for strict impartiality and political neutrality. A choice of two versions of the BBC we all know, both of them equally long-standing and authentic – but which would win out?

For a long time it wasn't entirely clear. The BBC's coverage of the referendum was certainly inadequate but at least the lack of interest from network producers meant that BBC Scotland's best journalists were able to fill up the space that was left, with an imperfect but tolerably knowledgeable and balanced handling of the campaign.

That was bound to change abruptly when YouGov published a poll showing the Yes campaign in the lead for the first time, leading to the London establishment unleashing the forces of hell upon Scotland, in an attempt to terrorise the country into rejecting self-government.

Perhaps naively, I actually had a fair amount of confidence that the deeply ingrained culture of neutrality at the BBC would win out at this crucial junction in the history of its relationship with the people of Scotland.

We've seen before, not least during the Hutton saga, that the corporation is capable even of broadcasting output that is excruciatingly embarrassing to itself, if that's the price that has to be paid to be seen as impartial. So I suspected that when BBC network producers and journalists suddenly woke up to the fact that a big story was unfolding in Scotland, they would bend over backwards to be seen to give the pro-independence case a fair crack of the whip.

I couldn't have been more wrong. With every passing hour, the sickening realisation dawned that journalists such as Nick Robinson were only decamping to Scotland to be active participants in the London establishment's Iraq War-style "shock and awe" campaign.

Indeed, the former BBC journalist Paul Mason, who now works for Channel 4, commented that he hadn't seen the corporation operating in such all-out propaganda mode since the invasion of Iraq.

The requirements for balance were only upheld in the most nominal of senses, with the Yes campaign being given roughly the same amount of airtime to defensively respond to the endless succession of scare stories that the No campaign had been given to pursue the scare stories in the first place.

There was no meaningful scrutiny of the credibility of the scares, nor was any serious attempt made to balance them out by putting the No campaign on the defensive over the legitimate fears people have about the consequences of giving up – possibly forever – Scotland's golden chance to choose its own political direction.

A \'Yes\' supporter with a tattoo of Scotland on his back holds a Saltire flag at a rally outside the BBC in Glasgow, Scotland September 14, 2014.
A \'Yes\' supporter with a tattoo of Scotland on his back holds a Saltire flag at a rally outside the BBC in Glasgow, Scotland September 14, 2014 Reuters

Even the few positive elements of the No campaign's script seemed to be lapped up unquestioningly by the BBC. The London parties must have thought all their Christmases had come at once when they heard their incredibly minor proposals for further devolution being repeatedly called "Devo Max".

For the avoidance of doubt, the correct definition of that term is "the maximum amount of powers for the Scottish Parliament that is possible within the context of a single British state". Could any serious journalist study the proposals in detail and then conclude that the name they had applied to them was remotely justified?

And then, of course, there was the now-notorious incident in which Alex Salmond gave a seven-minute long reply to Nick Robinson at a press conference, which was edited with appalling cynicism in the evening news to simply show Robinson asking his question, followed by a voice-over claiming that "he [Salmond] didn't answer".

To their credit, BBC Radio Scotland allowed the respected journalist Stuart Cosgrove to take to the airwaves and castigate the corporation for the woeful failings in its coverage of the campaign. He took the time-honoured line that lessons will have to be learned – well, that's fine if it's a Yes vote and we can be sure that the lack of impartiality didn't affect the result, but what if it's a No vote?

The Yes campaign have made clear that this is a "once in a generation" opportunity to vote for independence, so if the BBC takes stock after a hypothetical No vote and realises how badly it has failed the electorate, it's not as if it can order a re-run of the referendum on a more level playing field.

In those circumstances, the BBC and the vast Yes-voting public would somehow have to co-exist uneasily within the same state.

At present, the corporation seems to think it can deal with this problem by passing off those who recently demonstrated at their Glasgow headquarters as a bunch of cranks who are the enemies of free journalism.

I've got news for the BBC – those cranks represent a large, newly politicised segment of the electorate who have enough facts at their disposal to spot thinly-disguised propaganda when they see it. They're not going to be easily reconciled in the event of a No.

It's no exaggeration to say that the BBC's relationship with segments of the Scottish population may be about to break down as seriously as the Sun newspaper's relationship with the people of Liverpool did after the Hillsborough tragedy.

It's quite a poser – just what does a public service broadcaster do when it loses the confidence of the public?

James Kelly is author of the Scottish pro-independence blog, SCOT goes POP! Voted one of the UK's top political bloggers, you can hear more from James on Twitter:@JamesKelly