Leading article: The real issue is not the leader's age, but aptitude

Things are not looking good for the Liberal Democrats. On the eve of what promises to be a tricky annual conference, their ratings in the polls have slumped to what they were at the height of the debacle to remove Charles Kennedy as party leader. They have just 15 per cent of voters behind them, well below the 23 per cent share of the vote recorded at the last general election. They did poorly at the last local elections. And there is a sense that they are being squeezed between the Brown Bounce and the Cameron Bubble as Labour woos back disillusioned supporters and the Conservatives continue their two-steps-forward, one-step-back progress towards the centre.

Worst of all, the Lib Dems have in Sir Menzies Campbell a leader whose personal ratings are even more dire than those of his party. A poll yesterday showed that just 4 per cent of voters think he would make a good prime minister compared to 17 per cent for Cameron and 39 per cent for Brown. A BBC poll showed that a quarter of Lib Dem constituency associations are unhappy with their leader, who faces criticisms that he does not have the zing – or at 66 is just too old – to take the party forward. There have even been public expressions of discontent, albeit tactfully veiled: Chris Huhne, runner-up for the leadership last time, suggesting that Ming was not making enough impact, and Lord Rogers, the former Lib Dem leader in the Lords, voicing fears that the party was "suffering a lack of energy and an absence of direction".

The Lib Dem leader is only 10 years older than the prime minister but he appears to be from another age. In response to the criticism, he will pose with his grandsons in a party political broadcast to coincide with the conference. What would make more sense, however, is to make a virtue of his status as an elder statesman.

Downing Street may be trying to spin that Gordon Brown's attitude to Iraq is different from Tony Blair's, but the fact is that the Prime Minister supported his predecessor's decision to launch the war; Ming Campbell, meanwhile, opposed this foolish misadventure. David Cameron's Quality of Life policy group may have burnished his party's credentials on the environment but the Lib Dems have an honourable record of being clothed in green before it was fashionable. The party does have electoral distinctiveness.

The harsh truth is that Campbell has failed to project a distinct liberal agenda. This is not an issue of his age, but of aptitude. And with Labour and the Tories squabbling over similar territory, Britain badly needs a radical voice. Ming Campbell must provide that. He needs to spell out the policy implications of his claim that the rich have done "too well" under Labour, and say how he will redress the issue. He needs more freethinking proposals like his "pupil premium" plan to spend £8,000 a year – the cost of a year at a private school – on educating every disadvantaged child. He needs to clarify his woolly proposal for a referendum on whether Britain should stay in the European Union, rather than having a vote on whether the UK should sign up to the latest EU treaty.

Above all, he needs to play out his instinct that the great division in British politics now is not between left and right but between liberal and authoritarian. He needs to set out clear options in defence of civil liberties and curb plans by his ambitious home affairs spokesman, Nick Clegg, to announce a tougher line on immigration this week. And he needs to proclaim his firm belief that "nothing is more important than climate change".

The joke doing the rounds among the Lib Dem disgruntled is that "Ming can only get better". This week their party leader has to show that not only is this true, but that he can convince the nation of it too.