A Greenpeace advert that was banned last year over claims that fracking wouldn't cut energy bills wasn't misleading, the UK's ad watchdog has now admitted—in a rare reverse ruling.

The Advertising Standards Authority said on Wednesday that it was wrong to have admonished Greenpeace over its press ad, which stated: "Fracking threatens our climate, our countryside, and our water. Yet experts agree—it won't cut our energy bills."

Lord Lipsey—who was a member of the economic affairs committee from 2009 to 2014—challenged the claim by arguing that it was misleading and unsubstantiated, and his complaint was upheld by the regulator in May last year.

But the ASA has now accepted that it made a mistake in its earlier ruling, which Greenpeace described at the time as "bonkers."

The then-prime minister David Cameron had claimed that fracking would help cut Brits' energy bills, which prompted Greenpeace to challenge that assertion with its press ad. The environment activist group had called on UK citizens to "stop the government's plan to allow fracking firms to drill under your home without your permission." And it backed up its claim by citing experts.

"We acknowledged that among the material Greenpeace had provided, there were quotations indicating clearer support for the view that fracking would not reduce prices," the watchdog said in its reverse ruling.

The ASA added: "While a range of more conditional expert views also existed, the general consensus among most appeared to be that a meaningful reduction in UK domestic energy bills was highly unlikely and/or was limited to a small number of potential scenarios. We therefore considered the claim as it was likely to be interpreted by readers had been substantiated and was not materially misleading."

Quite the reverse ferret, there. Or, to stick with the fracking theme, the ASA just plastered over a badly drilled hole in its ruling.

Listing image by Greenpeace