When I asked Nick Clegg at his joint press conference with Mahmoud Abbas about the increasingly combative nature of the UK government's language on settlements, I didn't expect him to escalate the rhetoric still further.

His description of new building as an "act of deliberate vandalism" sent a frisson through the room and President Abbas was visibly surprised. He later expressed his delight that this was the sort of language he had been waiting for from the British government.

His words were in marked contrast to those of the Prime Minister, who expressed his displeasure at Israeli government action in far less provocative terms in his official statement later in the day.

It has long been the UK's position to oppose settlement-building but, as Development Minister Alan Duncan discovered when he used the phrase "land grab" last year, language is everything when dealing with such a sensitive issue.

Foreign Office officials have in recent weeks shown a growing frustration with the Netanyahu government and a matching intensification in their language. The term "aggressive" is now often attached to settlement building and officials have also been heard to describe housing developments across the Green Line as "deliberate vandalism", the very phrase used by Nick Clegg.

It is now possible to see a genuine fissure opening up between Cameron's Downing Street, which accepts the argument that it is not always helpful to push the settlement issue in Mr Netanyahu's face, and the Foreign Office, which believes continued settlement-building could derail peace negotiations. Some believe William Hague has now "gone native", with the Deputy Prime Minister also falling in behind the Foreign Office line.

The coalition has often used its "creative differences" to good effect. It is difficult to accuse the government of splits when disagreements are explicit. On foreign policy this can be risky but, so far, the profound disagreement between Nick Clegg and David Cameron on Europe has not caused undue political damage.

The same may prove to be the case with Middle East policy, simply because foreign affairs interest the general electorate little - short of going to war. And Tony Blair was re-elected even after the Iraq invasion.

But there is a broader point. Britain has become increasingly marginalised in negotiations in the Middle East. Why should any of the parties there take us seriously if our own politicians can't even agree on the language to use about this most fundamental issue?