During October last year, unwarily dozing listeners to BBC Radio 4's Today programme had an unsettling experience. It was conference season and Sarah Montague was presenting a piece comparing the two main parties by testing out their marquee offers to the nation on some ordinary punters. So far, so predictable. The tone of her report, though, was very strange indeed. Marching around Walton West in Merseyside, Montague took it upon herself to strongly disagree with anyone she encountered who quite liked the sound of an energy price freeze. Wouldn't they rather, she wondered, be given some help to buy their own homes? As the report progressed, Montague became ever more strident – to the point where it began to sound less like an even-handed presentation of both ideas and more like implacable advocacy of one over the other. She even managed to change a few minds – George Osborne must have been delighted to hear one of his flagship policies promoted so enthusiastically on the BBC.

Claiming that the BBC swings to the left is the oldest trick in the right-wing media playbook. And even allowing for the fact that the idea is usually both perpetuated and swallowed by the kind of people who also claim that white, straight, middle-class males are a persecuted minority in Broken Britain, it's not an immediately outlandish proposition. After all, what kind of person admires the underlying concept of the BBC enough to want to work for it? Probably someone who values large-scale, publicly-funded, slightly paternalistic state enterprise, for a start. Certainly, a promising right-leaning news journalist may well be happier over at Sky where the money's better, the print media scrutiny all-but non-existent and the bureaucracy less agonizingly glacial and labrynthine.

All the same, the last few years have suggested that the direction of any BBC political bias is far from obvious. Andrew Neil (a confirmed admirer of Margaret Thatcher and a former employee of the Conservative party) and David Dimbleby (a former member of the Bullingdon Club) remain two of the corporation's biggest current affairs beasts. Then there's Political Editor Nick Robinson (a former President of the Oxford University Conservative Association) and Montague herself (a former stockbroker and bond trader who has crossed two NUJ-sanctioned picket lines since her arrival at the BBC). Plenty of the programming, too, has reflected an increased willingness to cheerlead for the government agenda. John Humphrys, for example, offered up The Future State of Welfare in 2011; the documentary seemed to enthusiastically underwrite a 'skivers versus strivers' narrative and was duly endorsed as 'thoughtful and intelligent' by Iain Duncan Smith. The programme was later criticised by the BBC Trust for breaking impartiality guidelines.

Since David Cameron became Prime Minister in 2010, the general ambience surrounding the BBC has subtly changed. Partly, this is a coincidence of circumstance; the BBC remains the nation's broadcaster of record and this is probably a burden as well as a privilege - consider the audio-visual red, white and blue bunting which the BBC is obliged to flutter during events like 2011's royal wedding. However, it's a duty that the BBC has accepted with great alacrity in recent years. The Beeb has become home to all manner of heritage-led, cod-patriotic kitsch. A flurry of films celebrating Our Brave Boys And Girls serving overseas is one thing but the likes of 2011's Harry's Arctic Heroes are another matter entirely. Documenting what was probably best described as a turbo-charged version of a Duke of Edinburgh Award jolly, this series managed a terminal velocity level of deference, combining Royalty and injured servicemen to conjure some sort of perfect storm of Middle-England pacifying TV catnip.

There's probably an informal but rigorously maintained ratio of what might be described as Deference TV. After all, as the perfect conduit between the dangerous subversives at Broadcasting House and the actually-very-noisy-indeed silent majority in the Shires, it's probably for the best that Fiona Bruce continues her Home Counties outreach programme. What's changed is the surrounding context. The BBC used to take risks too. It's easy to forget that even in its very recent past, BBC4 brought us Mad Men and The Flight of the Conchords, while BBC2 gave us The Office and The Day Today. Just as the current affairs coverage has acquiesced to the line of least resistance, so has much of the comedy and drama; it's hard to imagine an emergent 2014 Chris Morris or Stewart Lee gaining any traction in the current Beeb-scape. Not in the comfortingly apolitical era of Miranda, Not Going Out and Mrs Brown's Boys.

Even so, this evidence of rightward drift still feels circumstantial and anecdotal. But it is possible to put some additional meat on the bones. Last year, the New Statesman ran a piece by Cardiff University lecturer Mike Berry which offered an intriguing analysis of current affairs trends at the BBC. Berry had been involved in a research project funded by the BBC Trust. Firstly, it suggested that Conservative voices outnumbered Labour ones by a ratio of four to one during a sample period in 2012. Given that the Conservatives are the current party of government, that's perhaps not too surprising – until it's compared with a 2007 sample period during which Labour representation beats Conservative by only two to one. Then there's union representation. In the same two sample periods, business representatives outnumbered trade union spokespeople by more than five to one in 2007 but by 19 to one by 2012. Given the power that unions are still perceived to wield, that's peculiar. The report's study of the weeks surrounding the financial crisis is also illuminating. The airwaves were overwhelmed by the voices of bankers, hedge-fund managers, stockbrokers and other 'city sources' – and so, the terms of the debate were framed.

So is the BBC biased to the right? Maybe, maybe not. What seems certain, however, is that it's increasingly and instinctively willing to dance to any tune being played by the government of the day. Particularly when, as is currently the case, that government is led by a man who has described the prospect of cuts at the BBC as "delicious". Director General Tony Hall's increasingly desperate defence of the BBC's funding suggests he's starting to think a 'top slicing' and sharing between broadcasters at least, might be a distinct possibility. After all, since the dawn of Cameron, the BBC has been forced to fund the World Service from within its already attenuated budget - a decision that led directly to the recent shelving of BBC3.

Those generally sanguine about the disappearance of the BBC's flimsy youth wing should consider the implications of BBC3's axing more carefully, because it's entirely of a piece with one of the most objectionable tropes of the coalition's wider strategy. Is there a single strata of society doing worse out of the Cameron Project than the young? This latest blow represents yet more ruthless targeting of the powerless - it's just that this time, the government has diverted the cause and effect downstream and found someone to do their bidding for them. Presumably, there's an assumption at the BBC that the consumers of Lee Nelson's Well Good Show and Two Pints Of Lager And A Packet of Crisps will be less likely to kick up a meaningful fuss than lovers of Jonathan Meades and Storyville. Based on the BBC 6Music furore, it's probably a correct assumption, but that doesn't make it any less ignoble. In any case, viewers should be under no illusions that the axe doesn't still hang over BBC4 too.

So does death by a thousand cuts loom? Well, yes. The best way for the BBC to guarantee this kind of lingering, painful death is to proceed exactly as it is - quiescent, conservative and increasingly indistinguishable from its competitors. It's time for the BBC to draw a line in the sand, stop apologising for its own best qualities and launch a counterattack. It's time to ask the public what, exactly, they believe the purpose of the BBC to be. When the BBC is doing its job it is, by definition, right up in the face of whoever currently holds the keys to 10 Downing Street. If this means being called left wing, so be it – the position is easily defended and entirely consistent with the BBC's history; as early as 1926, the Beeb was damned for refusing to do the government's propaganda bidding during the General Strike. Because it's not meant to be Pravda, is it? It stands aside from governmental fear or favour and that's the whole point of it. The Beeb was much frailer back then; newer, less totemic and accordingly, more vulnerable. And yet here it still is. You could almost be forgiven for thinking that despite the endless, negative briefing, people quite like it.

The last time the BBC seriously challenged a British government was during the 'dodgy dossier' affair of 2003. And while that unfortunate sequence of events must have shaken the corporation to the core, if the BBC fails to interrogate our rulers from as independent a perspective as possible then, regardless of the bleatings of its numerous print media enemies, it's short-changing its shareholders (us) and not doing its job. It's time for the BBC to stick up for itself. The Daily Mail may have discerned left-wing bias in a recent episode of Sherlock. But The Daily Mail could probably discern left-wing bias in Mein Kampf if it really put its mind to it. Despite its recent batterings, the BBC is still, broadly, cherished by the majority of Britons. If it fastens its courage to the mast, it can stay that way. But the fightback needs to start now.