The new arm, Leith Direct, has been set up to provide Leith London with alternative revenue streams by offering clients a choice of either direct-only solutions or fully integrated campaigns.
The initiative will be run by Helen Lardner, who will head the client services side of the business, and the creative director, Gareth John.
The new Sony business comes with Lardner and John from their previous agency, Langham Works (previously called DLFC), and was won without a pitch. Leith Direct has also picked up one other, undisclosed client.
Lardner has spent the past two years as a direct marketing consultant for agencies including Langham Works and Swordfish.
Before this, she worked at OgilvyOne, where she ran the Royal Mail account, and HTP Wunderman, where she ran the Ford of Britain business.
Lardner and John first teamed up at Langham Works on campaigns for Tesco Personal Finance, DFDS Seaways and Sony Europe.
Jeremy Pyne, the managing director of Leith London, said: "We're delighted to have found such a strong and well-proven team to form the foundations of our direct offering. We look forward to developing more direct-only opportunities for Leith London, as well as offering all clients access to an integrated service."
Lardner said: "We like the friendly and open approach that Leith takes and we're looking forward to generating more exciting opportunities together in the future."
The announcement follows news two weeks ago that Mike Cornwell, the former TBWA\GGT chief executive, is in talks with Mother with a view to launching a DM agency.