The PR offensive is targeting senior executives at ad firms, around 150 of whom have now been sent postcards carrying images of flyposters on buildings, with the message 'The West End should look better than this'.
The media relations campaign also focuses on attempts to prosecute firms placing illegal flyposters. Last week Westminster successfully prosecuted sportswear chain Footlocker for five offences.
Another set of postcards flag up Footlocker's fine of £2,000, stating 'Not only is it unsightly, but it could prove costly for your clients', has also been sent to ad execs.
The campaign is backed by the Advertising Association.