After weeks of speculation, LibDem leader Charles Kennedy yesterday threw down the gauntlet to his critics. But, on the back of his party's best election result in 80 years, why have they got it in for him at all? Nick Morrison reports.

CHATSHOW Charlie, Good Time Charlie, even, perhaps cruelly, given yesterday's admission he suffered from alcohol problems, Champagne Charlie. For all his electoral success, the LibDem leader has never managed to shake off the accusation that he is a lightweight.

To his supporters, his appearances on Have I Got News For You, his approachable style, his willingness to joke at his own expense, are a sign that Charles Kennedy is a normal bloke, a "fully paid-up member of the human race," in the phrase he loves to quote.

To his detractors, they are proof he lacks depth, he is too frivolous to lead a major party. While he may be the leader everyone would rather have a drink with, even if just a cup of tea, he is not the one they would rather was prime minister.

But Kennedy seemed to have answered his critics in the best possible way: through electoral success. In the two general elections since he succeeded Paddy Ashdown in 1999, Kennedy has increased both the LibDems share of the vote and the its MPs.

In 2001, the LibDems got 18 per cent of the vote, up 1.5 per cent on 1997, and 52 seats. Last year, the vote rose to 22 per cent, and the number of MPs to 62, the best performance by a third party in 82 years.

He has done this by abandoning his predecessor's policy of forging an alliance with Labour - a plan which lost any credibility after the 1997 landslide - and instead aiming for power through steady and gradual electoral success.

And he has also managed to carve out a distinctive position for his party at a time when competition for the centre ground has never been so fierce. Civil liberties, local income tax and opposition to the Iraq war, albeit muddied by subsequent support for the troops once the conflict began, have given the LibDems a clear identity.

In the Scottish Parliament, the party has been in coalition with Labour, and has been the driving force behind popular policies such as dropping student tuition fees and providing free long-term personal care for the elderly.

But this has not been enough for some. A whispering campaign against their leader has been gathering force within the party almost since the moment of their greatest triumph last May, reaching deafening proportions just before Christmas.

Yesterday's announcement, an admission that he has been battling alcohol problems and a challenge to his opponents to face him in a leadership contest, comes after the failure of repeated efforts to assert his authority and quell the speculation. These even included a warning, reported yesterday morning, that a leadership election would be "the most enormous self-inflicted distraction".

Now Kennedy is gambling, both that his most staunch critics will be unwilling to put their heads above the parapet, just as they were when the rumours reached fever pitch last month, and that his popularity among rank and file members would be enough to give him a comfortable victory.

But this then begs the question: if he has been so successful in electoral terms, and he is popular with party members, why is his leadership under threat at all.

The answer is threefold. First is the belief that however well the LibDems did at the last election, they should have done better. With the Conservatives seemingly weaker than ever before, and with an unpopular Government still dogged by the Iraq war, this was the time for the party to break through into the big time.

The LibDems have been told they are on the verge of power more times than Cyril Smith had hot dinners. From David Steel urging their Liberal predecessors to "go out and prepare for government" in 1981 to Paddy Ashdown on the brink of securing a seat at the cabinet in 1997, the party has had the promise of glory only to find it tantalisingly out of reach.

The Liberal magazine has been among Kennedy's chief critics, and editor Ben Ramm last month claimed that 3,300 party members had signed an on-line petition urging their leader to go, citing the "massive opportunity missed" at the last election as a principal reason for action.

The fear that such an opportunity may not come again ties in to the second reason Kennedy is at risk: the election of David Cameron as Tory leader.

If Cameron, as a young, dynamic leader with the vision and confidence to reshape his party, is putting the wind up Labour, he is also scaring the bejesus out of the LibDems. The worry is that by moving the Tories closer to the centre, Cameron will woo back those Conservatives who defected over the last 15 years.

This would continue a trend seen at the last election: while the LibDems increased their share of the vote, in head to head battles with the Tories they came off second best. The "decapitation" tactic, of targeting senior Tory MPs, was a resounding failure, the only scalp that of shadow education minister Tim Collins in Westmoreland.

If this is already a matter of concern, then Cameron's election will only make it worse. And if this were not bad enough, the new Tory leader's energy contrasts with Kennedy's more laid-back style, making him seem positively lethargic.

And finally there is the reason Kennedy bravely confronted at the start of yesterday's statement: his alcohol problem. His alleged drinking has been the source of countless rumours against him even before he won the leadership - in a resounding victory against one of those apparently plotting to succeed him, Simon Hughes, lest it be forgotten.

Cancelled appointments, his celebrated failure to turn up for the 2004 Budget statement, and his confusion over his own party's tax policies during the last election campaign, have all added fuel to the fire, that he is a man who likes a good time, but is unsuited for leading a major political party, much less for becoming prime minister.

Those who hoped his marriage to Sarah Gurling in 2002, or the birth of his first child Donald James during last year's election campaign, would see him dispel the rumours, have been confounded. Now, by his own admission, there is some truth in the stories, and his gamble is that he will be applauded for his honesty and courage rather than condemned for his drinking.

Despite Kennedy's successes, these factors have combined to create a feeling that he is not up to the job of leading the LibDems, and that, whatever his past achievements, he is unable to take the party to the crucial next stage.

But if his gamble is that he will win any leadership contest anyway, it is far from clear that this would be the end of the matter. Even though one of those most often cited as a possible leader - the respected foreign affairs spokesman Sir Menzies Campbell - was the first to announce last night that he would not be throwing his hat in the ring, the noise is unlikely to stop.

Kennedy is aware of a letter which has been circulating, signed by 11 out of 23 party spokespeople, declaring that they have no confidence in his leadership. Although it has not been signed by the three thought most likely to run - Sir Menzies, party president Simon Hughes and home affairs spokesman Mark Oaten - the fact that almost half his top team, and almost a fifth of his MPs, believe he should step down, may ultimately prove irresistible.

The contest is likely to be swiftly followed by local elections, and it may be that the electorate's verdict will have more impact than that of LibDem members. For if Kennedy thinks his gamble could yet restore his credibility, he should remember that the last party leader to make such a bold move was John Major in 1995.

He ended up roundly defeating his challenger, John Redwood, but the boost to his authority was only temporary. In the end, it was the voters who delivered the crucial judgement.

THE RIVALS

Sir Menzies Campbell

The 64-year-old deputy leader and foreign affairs spokesman is the LibDems' elder statesman in Parliament and one of its most authoritative voices on key issues such as Iraq and civil liberties.

Because of his age, the former Olympic runner - nicknamed ''Ming the merciless'' - is likely only to be a caretaker leader. It has been reported that he will only stand for the leadership if he is guaranteed to be selected unopposed.

Mark Oaten

The home affairs spokesman is a leader of the so-called Orange Book group of right-leaning Liberal Democrats and has made clear his ambitions to lead the party.

Elected to Parliament as MP for Winchester by a margin of just two votes in 1997, he transformed the constituency into a LibDem safe seat in a re-run poll and consolidated his position in the following two elections.

Oaten, 41, has a strong following among the LibDems' younger MPs in Westminster, but his support for a ''tough liberalism'' approach to law and order and alternative methods for funding public services may alienate left-wingers among the party's grassroots.

Simon Hughes

The LibDem president was defeated by Charles Kennedy in the battle to succeed Paddy Ashdown in 1999 and has made no secret of his intention to try again for the leadership, though he insists he will not stand against Kennedy.

As the LibDems' defeated candidate for London mayor and MP for Southwark North and Bermondsey since 1983, the 54-year-old barrister is on the left of the party.

He would be expected to win backing from activists who see the party's future in competing with Labour for the support of voters concerned about civil liberties and social justice.