The agency created only one campaign for the company, which ran pre-Christmas on TV, poster, print and radio.
"It became apparent over time that we had some major strategic and creative differences with Red Letter Days," Mother's Stef Calcraft said. "We took the only course of action that made sense for us. It is always regrettable when this happens and we wish it well in the future."
Media planning remains with Naked Communications and buying with Equinox.
Mother took the account in May last year after Red Letter Days also held talks with HHCL & Partners and St Luke's. It was hired to help build the company's profile in line with its bid to float on AIM.
Mother's campaign featured Santa Claus and his helpers getting bored having to deal with the usual variety of Christmas gifts.