There’s a tactical voting tool on the Telegraph website, which despite a somewhat loaded headline purports to even-handedly advise confused voters on the best course of action to take in their own constituency depending on whether they want to keep Ed Miliband or David Cameron OUT of 10 Downing Street.

We were a bit suspicious when we typed our Bath postcode in and asked to keep Cameron out, because it advised us to vote Labour even though it’s one of the safest Lib Dem seats in the country (with the Tories in 2nd) and Labour got just 3,251 votes in 2010, which is to say they’ve got absolutely no hope here.

And then we tried some Scottish seats, and things got a bit creepy.

Hmm.

There’s nothing illegal about a newspaper telling its readers to vote tactically, nor even in it giving them seat-specific instructions on how to do it. But this is something different. This is fraudulent. It’s claiming to be giving tailored advice, but actually just saying “anyone but SNP, no matter what the local circumstances”.

[EDIT: In fact, as you’ll see from a reader comment below, it’s hard-wired to do so automatically for any Scottish seat, although it works properly for the rest of the UK.]

But rather than angry, SNP voters should be delighted. Because what that means in practice is that in seats which are notionally Labour-Tory, Lib Dem-Tory or Labour-Lib Dem contests (eg East Renfrewshire or Gordon), would-be tactical voters are being given wonky advice which will in fact split the Unionist vote and help let the SNP in.

Nats had some fun at the weekend posting fake tactical-voting wheels for the loony “SNPout” group, to the point where their demented spiritual leader Jill Stephenson let out this primal howl of dismay:

But whoever got into the Telegraph office and sabotaged its source code like this is operating at a whole other level of subversion. We take our hats off to them.