The Advertising Standards Authority has upheld a complaint made by a Labour peer against a Greenpeace anti-fracking advert, but Greenpeace has labelled the decision "baseless, biased and bonkers".

Greenpeace ran a national press advert in January which opposed fracking. It read: "Fracking threatens our climate, our countryside and our water. Yet experts agree - it won't cut our energy bills".

Lord Lipsey challenged the claim that “experts agree – it won’t cut energy bills”, saying that particular statement was both misleading and unsubstantiated.

The ASA today said it had upheld his complaint and ruled the advert cannot be shown again in its current format.

Greenpeace have questioned both the impartiality of the ASA and of Lord Lipsey, who they claim is pro-fracking.

It said the chair of the ASA, Chris Smith, "has a second job as head of the Shale Task Force, a lobby group funded by fracking firms including Cuadrilla, Centrica and Total".

Greenpeace said that it challenged the ASA to provide evidence that experts disagreed with the statement. However the ASA said that the “onus of proving or disproving the statement is on Greenpeace”.

It cited an opinion from David Cameron, who wrote in 2013 that "fracking has real potential to drive energy bills down".

Greenpeace said that after its evidence was questioned, it provided quotes from 22 energy experts which supported the assertion made in their advert.

According to a statement made by the charity, these included: “the energy secretary, leading academics, and even three separate spokespersons from fracking firm Cuadrilla”.

Greenpeace UK energy and climate campaigner Louise Hutchins claims the ruling by the ASA sets a “very dangerous precedent”.

“An authority led by a fracking advocate has ruled in favour of a pro-fracking lord merely on the basis of the opinion of an avowedly pro-fracking prime minister. This decision is baseless, biased, and frankly bonkers.

“This ruling also sets a very dangerous precedent. The same perverse logic could be used to ban statements about evolution or climate change on the basis that someone somewhere disagrees with the mainstream view. We can’t allow the ASA to be used as a kangaroo court to muzzle dissenting voices on controversial issues like fracking.”

The ASA have said that the advert breached Committee of Advertising Practice codes: 3.1 (Misleading advertising), 3.7 (Substantiation) and 3.13 (Exaggeration).