The Sketch: Clarity is good, as long as it's clearly bad. Is that clear?

CLARITY IS a dubious quality in politics. The more of it you get, the harder it can be to make things out.

Yesterday, for example, the unfortunate Mr Davies insisted to the BBC's John Sergeant that he had made "a very clear statement" about the reasons for his sudden resignation on Tuesday.

Further interrogation about the unusual precedent he had set for the victims of street crime would be simply redundant, his tone suggested. He was both innocent and guilty and besides, the matter was in the hands of the police.

Mr Davies's interviewer coped manfully at this point; at very short notice he had been lead blindfold into a fog bank of unanswered questions and yet here he was being invited to admire the magnificent view.

It's true that the former Welsh Secretary was under considerable stress at this point - and, for obvious reasons, was unable to ease the pressure with a brisk walk across one of London's nocturnal wildlife reserves. That may have accounted for the mismatch between his adjective and the vapourous actuality.

But in his moment of trial Mr Davies had also fallen back on standard operating procedure - which is to pretend at all times that opacity is actually its exact opposite, a limpid translucence which only the wilfully short-sighted would find impenetrable.

The Prime Minister adopted similar tactics yesterday: "We have made it clear that it's sensible to wait for the Jenkins Commission's report" he replied to William Hague's third request for a yes or no answer on the question of whether he would deliver a referendum on electoral form in this Parliament. Why was it sensible?

Because nobody in their right mind whacks a wasps' nest with a stick before they are absolutely obliged to. But I don't think this was the kind of clarity the Prime Minister had in mind.

He simply needed something condescending to say after an effective dig from Mr Hague about his reticence on the matter.

"He envisages keeping a promise but he has to wait and see whether he's going to do so," Mr Hague had mocked, to cheers from his own backbenchers and a wry laugh from Mr Blair himself.

It was one of the best shots in a good session for the Leader of the Opposition, cheering Tories who had already been worked up by the tickle of a Labour scandal.

He gave Mr Ashdown a rap on the nose too, reminding Mr Blair during the follow-up to his first question that he wasn't the first Labour leader to have "a faithful dog called Paddy". Several Tory backbenchers proved that they are not just metaphorically barking by yapping "woof, woof" as Mr Ashdown rose to put a question on humanitarian aid for Kosovo. He growled at them magisterially, a St Bernard momentarily distracted from its mission by incontinent chihuahuas who had mistaken its back leg for a lamp post.

Mr Ashdown does have a clear policy at the moment - he wants to bomb Kosovo back from the stone age, using Nato planes to airlift aid to shattered villages. But clarity is a luxury he can afford.

Those in power, or more proximate to it, must continue to use the word as a kind of camouflage, a smokescreen which will keep the exact details of their movements from prying eyes.

Genuine clarity, the kind of crisp and brilliant light which conceals nothing, is only trained on the opposition. Towards the end of Prime Minister's Questions Mr Blair thanked one of his backbenchers for reminding him that he had been mistaken in what he had just said.

He had accused the Tories, several times, of having no clear policies on the economic downturn, but he had forgotten that they had made one specific policy commitment - to scrap Working Family Tax credit. When it comes to the opposition, you see, clarity is only good as long as it's clearly bad.

And I hope I've made that perfectly clear.