Andrew Marr, the BBC’s former political editor, said there is “an innate liberal bias” inside the public broadcaster.

Roger Mosey, once head of news, now director of sport, agreed that “in the past” the BBC had been “too closed to a wide range of views and we’ve had too narrow an agenda”.

So, is the BBC biased? In the past two years it has been hit with two critical reports, which endorse the conclusion that the Corporation failed to report Eurosceptic views fairly, and its coverage of business has been heavily criticised. There was also a complex report about the BBC’s Middle East coverage, whose text, although not its summary, indicated an antiPalestinian bias.

This already hints at a case to answer, even if the reality is complex – and the point was amplifed by the thoughtful document From Seesaw to Wagon Wheel, published on Monday. That was the source of the quotes from Andrew Marr and Roger Mosey, and critical analysis of several aspects of the BBC’s output, most notably its sympathetic coverage of the Make Poverty History campaign of 2005.

Mark Byford is the BBC’s deputy director-general, who sat on the steering group that looked at the report, and as chair of its journalism board, the man responsible for maintaining the Corporation’s impartiality. Try to ask him whether the BBC has a case to answer, and it is hard to get anywhere. Andrew Marr’s remarks, for example, are dismissed as “a quote from a seminar that was held several months ago,” and while Mr Byford is willing to concede that “he’s heard people say” that the BBC has a liberal bias, he does not accept it exists.

For Mr Byford the document is about something else, which is indeed one of its principal conclusions. Impartiality is “not about left and right,” but rather “its proposition has changed, it’s more complex” as people move beyond party politics to embrace causes. At the same time, the mantra does not demand bland, “balanced” programmes: the BBC “should allow more polemical pieces as long as they are clearly labelled” because it knows argument engages audiences.

Yet the final report repeatedly teases out examples where the BBC has reflected a narrower range of opinion than exists in Britain at large. The document asks, when, for example, was the last time Radio 4’s Today discussed capital punishment in a way that was in any way not hostile to the notion – or why politicians are treated completely differently to the spokesmen for pressure groups.

So could the BBC now air a “polemic” in favour of capital punishment? That would cause a stir. On this Mr Byford is hard to pin down: he argues that the BBC gives vent to a broad range of views “every week on Question Time”; that polemic would not be appropriate in news and current affairs, although “in a documentary there is a place for it”. But he does not agree that he should commission a bring back hanging documentary either.

There is also a complaint about how the BBC handled the Live 8 concert and Make Poverty History, with its march on the G8 summit in Gleneagles, which for all the party political consensus was highly political in that it called for debt cancellation.

Did the BBC go too far in its coverage of Live 8, which included related sympathetic dramas, including the Vicar of Dibley? This is a test of the new impartiality: did the BBC slip up and endorse an obviously liberal cause, because it was not subject of party political debate? Mr Byford says: “On the whole the BBC got it right,” by, for example, refusing to air the “click” campaign videos during the concert. He argues that “Live 8 is a national event that the BBC should be covering,” although as signatory to the report he accepts that the decision to air a campaign video as part of the Vicar of Dibley was a lapse.

Errors, of course, are inevitable in an organisation like the BBC with the sheer amount of output it produces. Mr Byford argues that the BBC is guilty of no more than that, but this is a debate that will not easily go away.

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