Six people challenged whether the claim could be justified and considered the ad, by Rapp, to be misleading.
The NSPCC said that in 2000 it conducted a study of 2,860 young adults, which revealed the "one in six" statistic.
The charity said the report showed that 16 per cent of the subjects had been abused aged 12 or under, which worked out to one in six children.
Although the study was dated 2000, its findings were still well-regarded and provided a good estimate of the occurrence of child abuse in the UK, the NSPCC claimed. A new study is due to be published at the end of 2009.
The ASA noted the outdated report findings and considered that people would interpret them to be derived from current statistics.
For this reason, it found the ad to be misleading and said it must not be shown again in its current form.