Leading article: Not a good career move, Boris Johnson

There have long been questions about whether Boris Johnson's position as elected Mayor of London is compatible with his authorship of a well-paid column in a conservative newspaper. But at least it might be said in his defence that he puts his views on the line and was upfront during the election campaign about how much he is paid (and pays in tax).

In suggesting yesterday – at the end of an article attacking the size and supposed editorial sympathies of the BBC – that the Corporation's next director-general should be "a Tory", on the grounds that "if we can't change the Beeb, we can't change the country", he has far overstepped any possible mark. The last thing the BBC needs is an overtly political director-general, of Labour, Conservative or any other persuasion.

What the Corporation needs above all is a respected professional – whether from the media, arts or managerial spheres – who understands the mood of the country and can carry the staff with him or her, while also being able to navigate the corridors of power. The authority of a director-general whose chief recommendation for the job was that he was parti pris would be undercut from the start, inside and outside the organisation. The Mayor's idea is a thoroughly bad one.

Now, Mr Johnson is known as a bit of a wag, and it is conceivable that he set out to make mischief, well aware that for the Mayor to say what he said was, to put it mildly, inappropriate. But Mr Johnson is no longer a student journalist. He is a senior elected politician with real influence and power, and spoken of – though he denies such ambitions – as a future Conservative leader and prime minister. His suitability for such a role was always in doubt. If he is serious about the BBC, those doubts are only compounded.