Mark Steel: The way they behave, they must want to lose the election

It's hard to find any other reason for insulting Joanna Lumley

Long ago the Labour Party decided to abandon its "outdated" values, to become obsessed only with winning elections. So it may have trashed its founding principles, but at least it became a master of how to win at the polls.

Which is why it's been able to carry out the classic election-winning strategy that goes: a) six weeks before the vote, get caught on secret cameras offering to do anything for Tesco or an arms company as long as they slip you a monkey, then b) before that's died down, publicly slag off Joanna Lumley.

All the great campaigners perfected this technique. Franklin D Roosevelt always fought on the slogan "Give us two grand and I'll do anything, I mean ANYTHING". And Gladstone started every speech during election campaigns with "Oi, Lumley, say that to my face, you slag."

One explanation for this strange behaviour might be that they've been paid to throw the contest by a Far East betting syndicate. Because it's hard to find any other reason for accusing the adored Joanna Lumley of being "silent" about the plight of the Gurkhas, when she was the most vocal campaigner for them, against the government now complaining she's silent.

Gordon Brown has apologised, but his next statement on the matter will go "And I tell you who else has been silent – Sir Steve Redgrave. Oh, it's different when there's a gold medal in it, then it's chatter chatter splash splash, but on this issue nothing. He makes me sick."

Then Alistair Darling will agree to be interviewed on Blue Peter, and say: "The way the economy works is you encourage businesses to invest, to stimulate growth, and I'll illustrate that by setting fire to a puppy."

Jack Straw will be caught on CCTV stealing a packet of éclairs from a petrol garage. And Brown will begin his first TV debate by saying: "Before we start with the politics, have a look at this," then drop his trousers and say: "I've had that rash a week now, does anyone know what it might be?"

But the Tories keep finding ways of proving themselves just as useless. Their current plan appears to be to make something up every day. So Cameron has suddenly announced a penny off national insurance, made possible by £6bn of cuts he's just thought up, that will come through "Efficiency".

But this obviously came out of nowhere, and he might as well have chosen any random words, boasting: "We'll make a further £9bn of cuts through gravity, and another billion through paranormal activity and a bit more behind square on the off-side and you'll be paying hardly any tax at all."

Next week he'll suddenly say to Paxman: "I've got it. We'll get a cheaper army. I bet the Chinese will send us one for half the price we're paying. Then we can cut VAT by, I don't know, ten or something."

The tax-cut theme seems to be part of his plan to randomly introduce policies that have worked for the Tories before, which is why immigration has suddenly popped up. Two days before the vote he'll announce we're leaving the Gold Standard and going to war with the Zulus.

So maybe they're both being paid to lose by gambling cartels. Which is why Labour hit back by bringing in the discredited Blair to campaign for Brown. They might as well say: "We are proud to announce our latest supporter, Peter Sutcliffe", and have a video-link of him in his cell saying: "At least I'm only the Yorkshire Ripper. If Mr Cameron gets his way he'll rip up the sound recovery that Gordon Brown has begun that will lead this country back to prosperity."

The result of this is that they are all despised equally, even the Liberal Democrats, whose manifesto should begin: "This country is sick and tired of two identical parties squabbling over nothing. What the British people need is THREE identical parties squabbling over nothing."

What makes this so frustrating is there's widespread contempt for the bankers and the high-level fiddlers, and anyone who led us into the war in Iraq. In a few cases, such as Respect's Salma Yaqoob in Birmingham, or the Green Party's Caroline Lucas in Brighton, candidates who've campaigned on these issues have won enough credibility to stand a good chance of winning.

But nationally the major parties have all supported the crooks and warmongers, and we've got six weeks of them going on like this, so if the Liberal Democrats were smart, they would take this opportunity to bring back Charles Kennedy as their leader. Except instead of hiding his drinking they could celebrate it. During the TV debates he could be sick across the stage, and the whole country would go: "Do you know, what he said was exactly what I was thinking."