WHAT is it about the Labour Party that makes it so mindlessly self-destructive?

No sooner had they been through the traumatic resignation of Scottish leader (or should that read "branch manager"?) Johann Lamont, than Labour plunge Ed Miliband's leadership into crisis by undermining him in the media.

And no, this is not just got up by the right-wing press. This is another classic case of Labour factionalism and in-fighting. It is mad party disease.

Of course, Conservative newspapers are hostile to Miliband. Cartoonists portray the Labour leader as a bumbling Wallace, without Gromit. But the press barons have not caused this crisis. Labour MPs have been telling anyone and everyone that Ed is a dork who can't eat a bacon sarnie and needs to be dumped before Christmas.

"Senior Labour sources" - meaning former Cabinet ministers - have been telling journalists that there has been a "groundswell of anxiety on the backbenches" over the threat from Ukip south of the Border and the SNP north of it.

A letter was reportedly circulating in the Commons last week from disgruntled MPs, though it never actually surfaced. Yvette Cooper has had to deny claims that a group of Labour MPs is seeking to have her installed as leader before Christmas.

Miliband has been criticised over Labour's "existential crisis in Scotland", as Labour MP Diane Abbott described it on BBC TV on Thursday. And it is said that he doesn't relate to working-class voters in England, who are moving to Ukip.

The Labour-supporting New Statesman magazine added fuel to the fire over Guy Fawkes night by saying that Miliband was a "Hampstead intellectual" who didn't understand the "aspirations of the lower-middle-classes". This was rich coming from a magazine run by Hampstead intellectuals.

But by now the press was in full-scale crisis mode. Ed's gaffes - forgetting the name of Labour council leaders, giving the impression he thought the retiring Sir Alex Ferguson had passed away, forgetting lines in his conference speech - were recycled in videos on newspaper websites. Figures from Labour's past such as Jo Haines, former press spokesman for Harold Wilson, were unearthed calling for Miliband to stand down for the sake of his party.

Comparisons were widely drawn with Iain Duncan Smith - "the quiet man who turned up the volume" - who was briefly leader of the Conservatives in the 1990s. Then Miliband committed the cardinal error of giving an interview denying that there was a leadership crisis which, of course, only confirmed that there was one.

But this is craziness. No serious political party should be thinking of changing its leader six months before a General Election, unless he is caught in a financial or moral scandal. It is like saying to the voters: we're so useless we didn't notice we had a no-hoper in charge of the party until we started thinking of how we would try to persuade you to vote for him.

Anyway, there is no credible alternative. Ed Balls, the shadow chancellor, generates even less public affection than Ed Miliband. Yvette Cooper - Balls's wife - is capable but hardly a serious leadership contender, and neither is health spokesman Andy Burnham. They are still relative unknowns who would not be able to install ­themselves in the public mind in the short time available.

Everyone's favourite for best-leader-Labour-never-had is the affable Alan Johnson, the former health secretary. He might have been a serious contender. But he has long ruled himself out. What party gives its top job to someone who doesn't want it and says they can't do it?

And the truth is, Ed Miliband is not bad. He may be awkward, but he is manifestly sincere, intelligent and is much more impressive in person than he is on television, where his image has become so bound up with his alleged physical peculiarities that it has become difficult to see him properly.

He has bottle, too. He took on the Daily Mail over its claim that his father, the historian Ralph Miliband, was a traitor. He took on the energy companies by calling for a price freeze. He took on business by calling for an increase in the minimum wage and promising such a move in his conference speech.

Ed is described as a policy wonk, but that's fine if the policies are popular, and most of them are. His ideas for funding the NHS through "sin taxes" on tobacco, a mansion tax and closing tax loopholes is backed by more than 70% of voters, according to a recent Survation poll. Breaking up the big banks is long overdue. And while I don't subscribe to his plan to have as many young people going into modern apprenticeships as go to university, it is popular with voters.

So, unlike most political leaders, Ed actually has something to say. But there is no way he will get a hearing so long as his own people fuel speculation that he is on his way out.

And why are Labour MPs so bothered with his cartoon image? Most political leaders - certainly most successful ones - have quirks of character and a certain oddness, but that doesn't rule them out of office. Alex Salmond, heaven knows, has been portrayed for years in the press as an obese grinning buffoon in a kilt with blue paint on his face. But he remains arguably the most successful political leader in the UK, who took his party from obscurity to being the party of government.

How did he do this? Well, partly because he is a very clever politician and a great speaker. But Salmond's secret weapon has been party unity. His people don't spend their time grumbling about him to the newspapers.

So why is Labour so afflicted by this inability to unite, to keep it in the family? It's a mystery, but perhaps it has something to do with the long tradition in the party of ideological and organisational factionalism.

This goes back to the days when there were serious arguments about whether Labour was a Marxist party, that wanted state ownership as in the old Clause 4, or just a party that wanted reforms to liberal capitalism.

There were also tensions between the trade union wing of the party and the ordinary membership, which led to arguments about the block vote. Then there were the divisions over nuclear disarmament.

Most recently it has been between the Blairite "modernisers" who want to reform public services in a market direction and social democrats who don't. I suspect Ed's detractors are mainly former ministers and MPs who thought he should never have got the job in the first place; that it should have been his brother, David.

They want to ensure that Labour lose the election by a significant margin so they can prove that they were right and ensure his resignation. Then they will push someone from the right of the party - perhaps the business spokesman Chuka Umunna - to replace him.

We saw this kind of factionalism in Scotland when Wendy Alexander was brought down by press ­briefings from her own side in 2008. That this is senselessly destructive hardly needs to be said.

I believe that last week Labour lost the 2015 General Election.