The Advertising Standards Authority (ASA) ruled that the TV, poster and national press ad campaign, created by JWT, was misleading after it received one complaint from SCA Hygiene, which makes rival brand Velvet.
The Andrex TV ad aired in spring and summer last year and showed a series of dogs of different breeds and sizes, while a voiceover said: "Some are soft, some are strong and some are long. But Andrex is soft, strong and unbeatably long, so spend your pennies wisely."
The press ads contained the footnote "excluding longer lasting/double roll products".
Kimberly-Clark said that the Andrex product had 241 sheets.However, the ASA took into account the fact there were two other luxury toilet tissues with the same length rolls on the market, and two types of toilet tissue that were more than 10cm longer than the Andrex brand, though they only had 240 sheets.
The ASA said that the ads claimed the product was "unbeatably long", which it proved not to be, and banned them for being misleading.
In response to the ruling Kimberly-Clark issued the following statement: "Kimberly-Clark is aware of the recent ASA adjudication relating to its Andrex advertising which ran last year and is in full compliance with the ruling.
"We would never intentionally mislead our consumers. Andrex is known for its softness, its strength and its length, and it was these attributes that the advertising was designed to draw attention to."
Variations on the claim to be soft, strong and long have been used by Andrex for decades, though it changed tack with its animated puppy campaign 'It's the little things' at the end of last year.
A spokewoman later said the compnay has not used the 'unbeatably long' claim since the summer campaign. She did not rule out the possibility of Andrex changing the length of its rolls in order to be able to make the claim again.