The TAG Worldwide chief executive, Steve Parish, said: "It's about the growing demand for content. A lot of our clients are talking to us and saying they need a different way of creating that content."
The new company would handle both TV and internet advertising content.
Parish played down production industry speculation that the new outfit would target clients directly. "None of the discussions I've had have been based on that concept; clients would dictate that, not us. Primarily, we'd want to work with our agency partners," he said.
TAG has in-house joint ventures with a number of UK agencies, including Clemmow Hornby Inge, Publicis, Lowe and Mother.
In November 2005, TAG expanded its post-production offering, buying the facility Red and merging it with the post-production outfit Smoke & Mirrors, which it purchased two years previously.
In the six years since Parish took the helm of TAG, the company's turnover has grown from £12 million to £57 million.
Miller's previous company, Large, was formed out of the merger between Spectre and Stark Films. Miller retired from the industry in 2004 following the closure of Large.