COMMERCIALS for a popular household cleaner have been misleading the public into thinking it can make an "old penny good as new" in 15 seconds, watchdogs have said.

Television adverts showed an old coin looking as shiny as new after being dipped in the cleaner to help demonstrate how it would work on sinks and taps.

But the Advertising Standards Agency (ASA) said it was "an exaggerated claim" and that the advert was "oversimplified" and "misleading".

The ASA ruled: "The advertisement must not be shown again in that form."

Twenty-six viewers complained about the advert for Cillit Bang, a cleaning product made by German firm Reckitt Benckiser, whose European marketing arm is in Swindon.

It showed a dirty coin being held in Cillit Bang and emerging shiny and clean after 15 seconds. It said: "Look how it gets this old penny good as new."

But viewers said it would take longer than 15 seconds to clean an old coin. The ASA said that "old coins did not come out looking brand new" but accepted that when half a coin was dipped in Cillit Bang it came out "visibly brighter than the undipped half".

"However, we remained of the view that this did not substantiate the claim that Cillit Bang would get old pennies to look as good as new in 15 seconds," the ASA said.

Reckitt Benckiser, whose Dettol Foundation has given cash to many good causes in Swindon, and advertising firm JWT admitted the voiceover unintentionally "oversimplified the chemistry."