Fairy Liquid's age old claim that it lasts twice a long as other brands has been contested by its closest rival, Persil, who say that the latest ads for Fairy are false and their claims are unsubstantiated. But the ASA has overruled Persil, after they found that Fairy really DOES last twice as long.

Persil got in a lather over its new campaign, featuring the slogan 'Fairyconomy', and a picture of bottle of Fairy with an equals sign – followed by a photo of two bottles of the 'next best-selling brand.' According to Nielsen data, that brand is Persil.

Persil challenged the ads, saying that it was an unfair comparison, and no mention was made of the actual size of the bottle of Fairy.

But the ASA threw out the complaint, saying that Procter and Gamble could prove it: 'We sought expert advice on the robustness of the evidence provided by Procter & Gamble. The expert considered the test reflected the practices of consumers and demonstrated that Fairy lasted at least twice as long as Persil. On that basis, we considered the claims that Fairy lasted twice as long as the next best-selling brand had been substantiated.'

Is this the beginning of washing up liquid war? Will there be a Persil Challenge? Either way, things are going to get nasty, and er...bubbly.