His consultancy, which he claims is the first of its kind, will offer advice on what's good and what isn't about campaigns and how they can be best exploited.
The former Lowe Howard-Spink creative director and former Abbott Mead Vickers BBDO vice-chairman said he did not plan to produce creative work himself.
But he admitted: "Agencies will be suspicious of us and we'll be slagged off."
Marcantonio is teaming up with Steve Hobbs, a former Lowe creative services director and chief executive of AMV's Electronic Solutions to form the company, which will be called Marcantonio Plus Hobbs.
They say they will be able to announce a household name as its first client within a week.
However, Marcantonio insisted the company was not planning to undermine relationships between clients and agencies.
"I'm all for clients remaining faithful to agencies," he said. "But sometimes there's a tug-of-war over a piece of creative work and it could be that we can help overcome a client's objection to it."
Hobbs will advise clients on how to use new technology to exploit their creative work and save money.
A former Volkswagen marketer, Marcantonio's creative credits include Heineken, Hamlet, BMW and BT. He has also worked as creative director on General Motors for Interpublic and, more recently, headed the creative department at the Leagas Delaney office in Rome.