The TV advert, which was for an HP laptop, was accompanied by a voice-over that said the "Intel Core i3 processor means that all the things I usually do, I can do 35 percent faster" while on-screen text compared the processor to an unnamed Pentium chip.
The ASA asked the PC retailer, owned by DSGi, to justify the claims, following a complaint from a viewer
PC World said the figure came from Intel's own benchmark and the increase in speed was down to "multitasking because that was something that every laptop user would do almost continuously when using the advertised product".
However, the ASA said PC World "did not show against what baseline the increase had been measured, and no data was included to support that figure".
"Because we had not seen evidence that showed that the advertised product could carry out everyday tasks 35 percent faster, we concluded that the ad was misleading."
Under the ASA ruling, the PC retailer must not run the advert in its current form again.
See also: ASA acts on Twitter advertising