Labour's latest bid to make fun of Nick Clegg and David Cameron appears to have backfired.

Just two days ago, a party political broadcast depicting Nick Clegg being chased by a cat was criticised for being a personal attack rather than an elucidation of Labour policies. On Friday morning the latest attack advert was released - another assault on Cameron and Clegg's chumminess, labelling the PM and his deputy "two peas in a pod". It also contains the line "They put £450 extra VAT on your shopping bill." The slogan left them open to accusations of hypocrisy, as former Labour chancellor Alistair Darling has admitted that he was also planning to raise VAT.

It did not take long for political commentators and Twitter users to notice that most of the items in the image are zero-rated. This includes the peas, plus all of the other fruit and vegetables, the biscuits (ones with chocolate chips inside are zero-rated, whereas chocolate covered ones would be liable), the ketchup and probably whatever's in that mysterious silver tin. Some Twitter users created parodies of the billboard.

@paulwaugh here is mine pic.twitter.com/qN32cUERLs

— WelshRacer (@Welshracer) May 9, 2014

The only identifiable things in the advert that would be liable for VAT are the washing-up liquid, the bottles of soft drinks and the beer. The source of the £450 claim is unclear, but it is thought that it refers to a period of several years, since it would require spending £18,000 on standard-rated goods at the 20% VAT rate for it to add up to £450 extra.