Marsh is reviewing its client base and is prepared to "walk away" from unprofitable clients.
Speaking at an AIRMIC breakfast meeting at the London Underwriting Centre, MMC chief executive Michael Cherkasky said it was a tough decision but Marsh needed to look at all client relationships on "a commercial basis".
"I agree that client relationships must be built on long-term relationships and Marsh will continue to do that. But only on a commercial basis.
"We can only be your vendor if the relationship brings profitability to both parties. We should through our services help bring profitability but if we can't achieve that, then we can't help you."
He said that the company was ready to spin-off MMC Capital do "deal with any conflicts of interest".
"Clients will be able to choose to use the services and if you choose to hire us then we will stay long-term," he said.
He added that the company would "aggressively" compete against any rivals that continued to use contingent commissions or were not transparent.
"Transparency is everything. Our image is damaged we know. It is like bruise it will not be healed overnight but will take time. But we are prepared to communicate with clients more frequently, and offer an efficient and high value proposition."