When Lord Adonis wrote in the Independent this morning, urging Lib Dems to vote Labour tactically to keep the Tories out, I was no worse than amused. “Oho,” I thought, “Ha” and other noises. There’s very little any Lib Dem can do about the increasingly desperate scrabbling of fingernails on the vertical deck of the Bad Ship Labour except close their eyes and wince.

Then around about lunchtime the Prime Minister (in what may yet prove to be a monumental error) told Labour supporters they should vote tactically for Lib Dems where necessary. “Hrrrm,” I thought, “Fnnnuurgh.” Stop telling people how to vote, you cynical bastards.

And so it was that I was mildly irritated, but still, on the whole,  a bit amused. The reason it may be a monumental error is that it can only push people wavering between Lib Dems and Tories towards the latter. That’s the exact opposite of what Labour want. If Brown is trying to build a Great Big Liberal Left Alliance to Oppose Teh Evul Toriez, a la Liberal Conspiracy, he’s going about it in as ham-fisted a manner as we’ve come to expect of a man who regularly tells audiences of hardened political hacks how much he wuvs his wife. He has actually just made a Tory majority ever so slightly more likely. Of course, it’ll be at our expense, but what we lose on the swings we’ll gain on the roundabouts. If I were wavering between Labour and the Lib Dems, I can’t imagine being that impressed with these cynical messages. I think I’d probably think, “Well, sod you then.” The only net losers in this desperate manoeuvring are likely to be Labour.

All good clean fun. But now, like a sudden cat turd in the herb bed, comes this.

Gordon Brown today accused the Tories of turning their backs on their traditional stance of being tough on crime by refusing to support Labour plans for the DNA database.

Conservative proposals to remove all innocent people from the database – apart from those accused of the most violent crimes – would mean more criminals escaping punishment if they win the election, he said.

…Brown told a meeting of Labour activists at a community centre in Stevenage: “This is a big issue and a big dividing line at this election.

“I’m sorry to say that the Conservative party has turned its back on their tradition and said they will destroy that [DNA] data.”

He was joined by Linda Bowman, the mother of Sally Anne Bowman who was brutally murdered and her body raped on the driveway of her home in 2005. Her killer Mark Dixie was convicted in 2008 on the basis of DNA evidence which also cleared her boyfriend, who had just dropped her off, of the crime. Dixie’s DNA profile had been added to the database after he was arrested for a violent assault.

She said: “If it wasn’t for the DNA found on Sally Anne her boyfriend would be serving a sentence for a murder he didn’t commit.”

Bowman has previously suggested that the DNA database should include profiles of everyone in the country in a bid to solve crimes.

The home secretary, Alan Johnson, who was accompanying Brown today, said: “Linda Bowman is a remarkable and brave woman who has suffered the most unspeakable tragedy yet still manages to be a compassionate campaigner for good.

“As Mrs Bowman says, the use of DNA helps the police put the most dangerous criminals behind bars but can also exonerate the innocent.”

Did you see what just happened to you? Or rather, what would have just happened to you if you weren’t so smart and well-informed? (And just generally a pretty cool and all-round fabulous frood with great taste in blogs, actually. Fantastic jacket, is that new?)

On a casual reading, and if you were a casual reader, you would have come away with the very distinct impression that Sally Ann Bowman’s killer was caught and an innocent man saved as a result of the DNA database and that this  would not have happened under the Conservative p0licy of removing innocent people from that database. (Needless to say, this is also the Lib Dem policy).

But you’d be wrong as the murderer, Mark Dixie, was caught because he committed a violent offence and had his DNA taken, not because he was an innocent man already on the database. He was caught because he was caught, and that  is all there is to it. It has never to my knowledge been Lib Dem or Conservative policy that people charged with violent offences shouldn’t have DNA taken and checks run.

(And as it happens, Dixie already had a violent criminal record when he committed the murder, but his known crimes are so long ago (pre-1993) as to predate the database. There is just no criterion whatever on which his case is a justification for retaining the DNA data of innocent people.)

The boyfriend, meanwhile, has even less to do with the database. It appears from the article that he was simply cleared when his DNA was taken, compared with the DNA at the scene and found not to match. No need for a database to do that. The irony is that the poor sap is probably still on it.

And yet this hopelessly unconnected and unconvincing case is being  slyly presented by association as supporting evidence for Labour’s microchip-the-population project.  It’s so full of holes it’s just one great big bloody hole. It doesn’t stand up to even the slightest thoughtful scrutiny (though I suppose at this point we should remind ourselves that the audience were Labour activists).

This is just sick. Ghastly, gurning Gordon Brown is standing up there, side-by-side with the mother of a horribly murdered young woman, stroking his precious database and telling us utter lies. And these are the people who, only this morning, were picking their way delicately through the wreckage of Iraq, ID cards, reforms abandoned and promises broken, to suggest that we – the Lib Dems – had some sort of symbiosis with them. We’re all nice, sweet, lefty people really, aren’t we, they wheedled. Progresssssssive, they hissed.

I feel grubby. Get away from me, you loathsome, tragically corrupt little shits, and  get your clammy, undead hands off of people’s votes. Don’t insult people by asking them to vote for you in the morning, and then driving your great big state juggernaut over some of their dearest values in the afternoon and assuming they won’t notice your cack-handed deception. And stop pooing in my herb bed, I bet that’s you and all.