Their venture will have neither a name nor a permanent office. The pair, who launch with no business, see the venture as a means to exploit their experience in providing high-level creative problem-solving. But Barker warned: "We won't come cheap."
The new arrangement follows the end of Barker's "gardening leave" imposed after his exit from BMP in September last year, and also the completion of a project on which Leeves invited Barker to work with him.
The fashion for creative independents gained momentum in the late 90s as agencies outsourced more creative work. But the phenomenon failed to take off, as agencies feared the independents might steal their business and clients preferred the comfort of an agency relationship.
But Barker claimed the initiative was timely because agencies were finding it increasingly unfeasible to maintain the overheads of large and permanent creative departments.
"Paul and I have both been creative directors and know what it's like," he said. "Clients often want to explore more than one creative route.
We can not only solve creative problems, but also execute them with skill and flair. That's a good offering."
Barker, a creative with more than 20 years' experience, is best known for his partnership with the art director Rooney Carruthers, which spanned spells at Bartle Bogle Hegarty, WCRS and BMP.
They won acclaim for the work on First Direct, the launch of Orange, Haagen-Dazs and the award-winning "swimmer" film for Levi Strauss.
Leeves, a one-time creative chief of the then BST-BDDP, was a founding partner of both Tilby & Leeves and Miller & Leeves. Most recently he has been involved in the production of agency showreels and film title sequences.
Both Barker and Leeves will also continue working on individual projects.
Barker recently completed a novel and is writing a couple of screenplays.