Editorial: Only total transparency will do, Prime Minister

If there is one thing the Prime Minister should learn from the latest revelations about his text message exchanges with Rebekah Brooks, it is that suspicions about their unpublished communications are not going to go away. However harmless, however innocent the content, the drip-drip of such missives into the public domain will be interpreted as evidence that there is more, and that somewhere there lurks damaging information that is being deliberately concealed.

On the face of it, the texts published yesterday do not tell anyone anything that is not already known: that David Cameron and Mrs Brooks were friends who enjoyed the sort of cheerful banter that friends typically enjoy. Nor does Mrs Brooks's lavish praise for his conference speech have to be interpreted as anything more than flattery from an ally. There is nothing politically sensitive here, beyond further evidence of their country-supper relations.

It is common knowledge that Mr Cameron and Mrs Brooks's husband had known each other since their schooldays; known, too – from the couldn't-make-it-up saga of Raisa the retired police horse – that Mr Cameron and Mrs Brooks socialised in the Oxfordshire countryside where they both lived. They were neighbours as well as friends. And while their relationship, at a time when Mr Cameron was rising to become Leader of the Opposition and Mrs Brooks to become chief executive of Rupert Murdoch's News International, may have been useful to both, there need have been nothing untoward.

Suspicions persist for two reasons. The first is Mr Cameron's tendency to memory lapses – such as whether he had ridden Raisa – over his communications with Mrs Brooks. The second is that, as The Independent disclosed two weeks ago, Mr Cameron withheld private emails between himself and Mrs Brooks from the Leveson Inquiry after taking personal legal advice.

There are thus two separate caches of Cameron-Brooks communications. There is one that has been provided to Leveson – where publication reflects the judgement of the counsel to the inquiry about what is pertinent. Then there is a separate cache that the Prime Minister was reportedly advised he did not need to submit. The very existence of this second cache suggests – rightly or wrongly – that there is material that the Prime Minister very much wants to keep to himself. It also suggests that he has thus pre-empted a judgement that was perhaps for the inquiry to make.

Now it may be that none of this adds to what has already been published; that the messages really are strictly personal or merely corroborate the evidence of a friendship between the Leader of the Opposition and the head of News International that was, advisedly, placed on a more formal footing when Mr Cameron became Prime Minister. Or could they hint at something else? An unseemly professional cosiness, say, at a time when Mr Murdoch's News Corp was trying to take control of BSkyB?

The only way for the Prime Minister to dispel the suspicions is for him to release all the material in its entirety. If privacy is a concern, he could do this initially via a judicial third party. But the issue, at root, is trust, and Mr Cameron has only his own secretiveness to blame for the fact that his claims to openness are not fully believed.