An advert for a protein supplement has been banned for exaggerating the product's ability to repair muscle.

The MaxiNutrition television and YouTube ad showed people taking part in various sports such as boxing, swimming, rugby and cycling before a voiceover said: "During hard exercise, breakdown happens deep inside your muscle fibres. MaxiNutrition helps provide your muscles with the proteins they need to recover, helping make you stronger and perform better. MaxiNutrition proteins aid muscle recovery."

The Advertising Standards Authority (ASA) received a complaint that the ad's claims were not in line with those authorised on the EU register.

GlaxoSmithKline (GSK), trading as MaxiNutrition, said its references to muscle recovery were in line with approved claims that protein contributes to the growth and maintenance of muscle mass.

Although not all the products in the range included protein, those that did had sufficient quantities to permit the authorised claims, GSK said.

The ASA noted that the ads did not specify the products to which the claims applied and made general references to MaxiNutrition.

It said: "We understood the authorised claims 'protein contributes to a growth in muscle mass' and 'protein contributes to the maintenance of muscle mass' related to increasing muscle mass and maintaining it, rather than repair during hard exercise or recovery after it.

"We therefore considered the reworded claims were not likely to have the same meaning for consumers as that of the authorised health claims."

It added: "We understood that the claim 'helping make you stronger and perform better' did not appear on the list of authorised health claims.

"In conjunction with the visuals that showed successful performance, we considered the claim exaggerated the benefit of the advertised product."

It ruled that the ads must not appear again in their current format and added: "We told GlaxoSmithKline to ensure that they retained the meaning of any authorised health claims if they reworded them to aid consumer understanding. We also told GlaxoSmithKline to ensure future ads did not exaggerate the health benefits of a product."