Coalition relations are growing more fractious and sour. Even departments where the rapport between the Conservatives and the Lib Dems had been respectful, such as Justice, are starting to bicker publicly. Today the Mail splashes on a row between the two parties over knife crime, in the week of the stabbing of teacher Ann Maguire. Nick Clegg has refused to support mandatory minimum sentences for repeat knife offences, and the normally secret letters discussing the measures have made their way into the pages of a newspaper.

Only a few months ago, ministers and advisers thought things were going sufficiently well in most parts of the Coalition (aside from Education, which has long had plenty of dirty linen flapping about in public) that these sorts of letters, which are known as ministerial write-rounds, would probably stay private. They told me that a letter war would turn quickly into ‘mutually-assured destruction’ and that things would have to deteriorate badly for anyone to want to declare the start of such a war. But it looks as though tensions really are rising.

One of the most telling quotes in the Mail report is that Nick Clegg told the Home Affairs Committee, an internal but powerful committee of ministers which discusses all domestic policies, that ‘we haven’t discussed it and I am not going to have it discussed… I’m in charge of this committee – forget it’. Clegg’s chairmanship of this committee has frustrated ministers in other departments too, to the extent that the only way to get a policy going was to brief it to the press, cause a row, and then wheedle some concessions from the Deputy Prime Minister with the press on your side.

This raises a question of what might happen if the two parties continue to work together after the 2015 election. These letter wars are all very well as we approach the general election and the two parties are firstly keen to assert their separate identities and secondly a bit tired and ratty at the end of five years of collaboration. But there will need to be a refreshing of the machine of government after the election if there is another Con-Lib coalition. Otherwise the letters might continue to flap out of Whitehall offices.

Tags: Chris Grayling, Coalition, knife crime, Nick Clegg, UK politics