PARIS — The French finance minister, Christine Lagarde, was on a panel at the World Economic Forum in Davos this January when her usual smile turned into a frown. Next to her, Robert E. Diamond Jr., chief executive of Barclays and one of the most powerful bankers in the world, thanked regulators and finance ministers for their role in shaping a better environment after the financial crisis.

Ms. Lagarde looked him in the eye. “The best way for the banking sector to say thank you would be to actually have, you know, good financing of the economy, sensible compensation systems in place and reinforcement of their capital,” she replied, to a burst of applause.

Her straight talk has helped burnish Ms. Lagarde’s reputation as one of Europe’s most influential ambassadors in the world of international finance.

And now it is helping to make Ms. Lagarde, 55, perhaps the leading candidate to succeed her friend and colleague Dominique Strauss-Kahn as head of the International Monetary Fund. The process of selecting a new managing director may speed up now that Mr. Strauss-Kahn has resigned his post as the I.M.F.’s managing director to deal with charges of attempted rape, stemming from his encounter with a hotel maid in New York last Saturday.