To be called Watermill, the company will handle an undefined range of projects for clients. Their first tasks include writing a BBC sitcom, devising a new museum space, and putting together a book for the Halo Trust.
Miller said: "The communications landscape is changing, so we're going to fill in some of the gaps." He also added that they would be "churning out great ideas" from 1 January.
Waters joined Freud earlier this year, when the PR company bought DFGW, the ad agency Waters co-founded. Miller, meanwhile, has taken time out of the business after he merged Spectre with Stark in 2004. The pair met in 1999 when they worked together on "The Body Zone" exhibit at the Millennium Dome.
Freud's creative team continues to be headed by the executive creative director, Paul Melody.