The Liberal Democrat MP Tim Farron's outspoken and open comments on BBC Radio's World at One, in which he said that his party is providing "cover" for the "toxic" Tories, give a rare glimpse of the mindset of quite a few Lib Dem parliamentarians, many of whom are starting to think about their seats amid tumbling poll ratings.

Farron, to be fair, has always believed that the coalition is an awkward ideological fit, but a number of other Lib Dems at Westminster are beginning to wonder how their party will get out of its apparent identity crisis, and dread next year's local elections.

On the same programme, the Lib Dem deputy leader, Simon Hughes, admits that his party has struggled to outline "distinctive policies" so far. Which brings us to a wider point.

Where exactly are the Lib Dem cabinet ministers? Where is Chris Huhne? Indeed, where is Vince Cable? Do they feel scared to speak out? If so, David Cameron -- who held his first "political cabinet" today -- had better address the issue and grant them more space to express themselves.

The coalition is, as Hughes has said, a "risk". But it will only work if the Lib Dems in it have a voice. Otherwise, there will be many more Tim Farrons protesting out there.