Here is the Labour party’s latest attack ad against Zac Goldsmith, the Tory’s London mayoral candidate, in the form of a mock CV:

So much is wrong with this. The criticism of Goldsmith’s loyal voting record is the worst part.

The immediate suggestion is that Goldsmith has been too loyal, not enough of an independent thinker. A look at his Labour rival Sadiq Khan’s almost rebellion-free voting record is enough to undermine that. Khan even worked as a party whip in 2007-08.

So maybe the point is to highlight how Goldsmith has voted 90 per cent of the time with the Tories. Which is inherently bad, by Labour’s standards. The fact that Khan has been equally loyal to Labour is different, because voting with the Labour whip is the correct way to vote. But Labour and Khan’s campaign should not be taking for granted that London agrees with them, that it is a “Labour city”. Pointing out Goldsmith’s Tory-ness as a Bad Thing reveals this underlying complacency.

According to the press briefing accompanying the ad’s release, the attempt is to paint Goldsmith as a “serial underachiever” for failing to be promoted, in spite of his voting discipline.

But the reason Goldsmith (a good speaker, fairly well-known, looks fine on telly – ministers have been appointed for far less) has never been given a government role is because of his vocal criticism of David Cameron and the government on Heathrow, the Recall Bill, Europe, and other subjects. He may be loyal according to his voting record, but pointing out his lack of a government role just highlights how much of an independent voice he’s been.

Voting record aside, this advert also conveys Labour’s belief that Goldsmith’s privilege will turn off London voters.

Although a Labour source insists “we will never criticise Zac Goldsmith for being born into wealth”, criticism of his wealth is implicit in this ad. The quotation about “left money by his daddy”. Pointing out that politics is a “family business” for Goldsmith. The accusation of nepotism. The use of his full, undeniably posh, name.

This is a foolish path for Labour to go down. The election – and previous elections – taught us that voters vote positively, out of aspiration rather than envy. The country has voted twice for David Cameron. London voters have chosen Boris Johnson twice as their mayor. Tell the story of Khan’s working-class immigrant family background, by all means. But don’t waste an opportunity to do so by calling Goldsmith posh. It doesn’t work.