Labour's VAT tactical failure

Has anyone noticed the really odd tactical failure Labour has made with its VAT argument? I mean, I can understand why they're arguing that the Tory figures don't add up unless they secretly plan to hike VAT (the Tory tax rise of choice historically), therefore leading to the conclusion that the Tories are going to hike VAT.

Putting aside the logical fallacies that always appear when politicians argue, I "get it". From a purely political point of view it's a simple, effective and potentially devastating line to take.

However, here comes the but, if you're going to go down the line of trying to drip the idea into the minds of the electorate that the Tories are going to increase VAT, why would you not be prepared, absolutely instinctively, without hesitation, to rule out rising VAT yourself when asked by the media?

For the past decade or so, Labour have, like it or not, been very effective tactically and strategically when it came to pushing the Tories into corners and maintaining their own position. Yet now they seem to have completely failed. Instead of ruling it out, we have strange responses such as "we've never raised VAT in the past".

Now, I know that strictly speaking they have raised VAT from 15% to 17.5%, having cut it briefly, but essentially they're in the same position as before, so they havn't really "raised it" as such. However, why rely on the same logical fallacy that what has happened in the past is evidence of what will happen in the future?

Did they really sit around a table and think that they could credibly hold a line that refused to rule out VAT increases whilst simultaneously arguing that the Tories planned to rise it even though the Tory position is actually identical to theirs?

As tactical failures go it's pretty epic isn't it? If Labour had just said "we will not raise VAT" then their attack on the Tories would hold and get repeated by the media quite willingly. By refusing to rule it out, they've basically ensured that the media will cut through the bullshit and not give their line the time of day (with the exception of the Mirror natch!)