Co-founder James Watt described the group as "a gloomy gaggle of killjoy jobsworths funded by navel-gazing international drinks giants" after it advised bar owners and retailers not to place orders for BrewDog’s Dead Pony Club IPA after 8 July if its packaging was not changed.
The group was acting on a ruling by its Independent Complaints Panel, to which it referred concerns over the labelling of the 3.8% alcohol by volume drink after an audit last year.
The panel concluded that the line on the label, "rip it up down empty streets", associated the product with antisocial behaviour and that other phrases, "drink fast, live fast" and "we believe faster is better", could encourage consumers to drink the product rapidly.
Henry Ashworth, chief executive of the Portman Group, said the rules exist to ensure that humour is used responsibly.
BrewDog, which the Portman Group said did not make any representations to the panel, issued the following statement from Watt this afternoon:
"On behalf of BrewDog PLC and its 14,691 individual shareholders, I would like to issue a formal apology to the Portman Group for not giving a shit about today’s ruling.
"Indeed, we are sorry for never giving a shit about anything the Portman Group has to say, and treating all of its statements with callous indifference and nonchalance.
"Unfortunately, the Portman Group is a gloomy gaggle of killjoy jobsworths, funded by navel-gazing international drinks giants. Their raison d’être is to provide a diversion for the true evils of this industry, perpetrated by the gigantic faceless brands that pay their wages.
"Blinkered by this soulless mission, they treat beer drinkers like brain-dead zombies and vilify creativity and competition. Therefore, we have never given a second thought to any of the grubby newspeak they disseminate periodically.
"While the Portman Group lives out its days deliberating whether a joke on a bottle of beer is responsible or irresponsible use of humour, at BrewDog we will just get on with brewing awesome beer and treating our customers like adults.
"I’m sure that makes Henry Ashworth cry a salty tear into his shatterproof tankard of directors as he tries to enforce his futile and toothless little marketing code, but we couldn’t give a shit about that, either.
"We sincerely hope that the sarcasm of this message fits the Portman Group criteria of responsible use of humour."
Watt has courted publicity frequently, for example as mimicking Russian president Vladimir Putin in the picture above in February for a PR campaign promoting BrewDog's Hello My Name Is Vladimir beer, which poked fun at Russia for introducing a law banning "homosexual propaganda".