We recently came across a ruling of the Advertising Standard Authority, which seems to make the use of colloquialisms in advertising more difficult.
The ruling concerned the use of the word “mental” in a radio advert by Bognor Motors Ltd: “if you don’t go to Bognor Motors, you must be mental”. This was ruled to be in breach of BCAP Radio Advertising Code rule concerning good taste, decency and office to public feeling: section 2 rule 9.
The key is the possibility that the colloquialism is a pejorative term which could cause serious offence to some listeners.
This is also a reminder that there are a number of codes of practice on advertising.