The ad, which features the slogan Time To Go Massimo, was put up this morning on a hoarding right next to the East Stand.
A fans’ group paid for the protest following a crowdfunding campaign and is now planning to buy further advertising space around the ground.
But tonight it emerged that a law firm acting for United has contacted the ad agency responsible for the site asking it to take down the poster, saying it amounts to “harassment” of Cellino.
In an e-mail to City Ads Yorkshire, the Ward Hadaway firm said: “This poster has obviously been placed outside the entrance to Mr Cellino’s place of work so as to cause the maximum distress to our client.
“This exacerbates the quantum of harassment that is intended to be caused and is malicious.”
Ward Hadaway says City Ads Yorkshire should arrange the removal of the advert immediately and warns that, if it fails to do so, then a formal complaint will be made to the police and licensing authorities.
The law firm is also demanding to know exactly who hired the advertising space, saying: “If necessary we anticipate being instructed to obtain the appropriate court order to have you disclose this information and will seek the costs incurred in doing so from you.”
The poster features a cartoon image of Cellino with a red cross covering his face, and a selection of quotes from the controversial Italian businessman,
Among them are:
• In 2015-16, it we don’t go into the Premier League, then I’ve failed. You can tell me I’ve failed.
• If we sell the good players we are wasting our time.
• My dream is to keep a coach for 20 years.
The ad is the work of a group calling itself Time To Go Massimo.
A spokesman for the group said: “With so many fans frustrated at the Cellino regime, we wanted to hit the ground running following another unsuccessful transfer window.
“The generosity, tenacity and passion of Leeds United fans never ceases to amaze – in just under a week we have the funds in place to run a substantial advertising campaign to highlight why we feel it’s time for a change in ownership.”
The group also said it intended to use the ad campaign “to make it clear that a sizeable portion of fans have no confidence in the Cellino regime and are urging him to sell the club”.