The retailer hired a casting agency to find “extras” to appear in an advertising campaign on Youtube, Facebook and Instagram.
It said those appearing should be “proper working-class people, but not at all like the characters on Benefits Street”, adding, “they should not look or sound posh and should skew towards northern accents”.
The casting advert then added: “And nobody from Liverpool, please.”
Morrisons blamed a “third party casting agency” for the gaffe, which has caused a storm of protests from Liverpudlians on Twitter.
The supermarket, whose previous advertising campaigns include the long-running “More reasons to shop at Morrisons”, said it never made such a request to the agency.
A spokesman said: “We are angry and we apologise that a third party has published a statement using our name without our knowledge. Everyone is welcome at Morrisons and we work really hard to ensure our marketing represents the whole of the nation.”
The casting advert bore the name of London-based Casting Networks, which describes itself as a software company “dedicated to providing business solutions for entertainment professionals”.
Last year Morrisons’ new boss David Potts ended the company’s association with TV favourites Ant and Dec, who had been fronting the firm’s TV adverts. Former Top Gear presenter Richard Hammond also fronted a series of commercials.