WASHINGTON  The chairman of the Federal Reserve, Ben S. Bernanke, called on Tuesday for a broad overhaul of financial regulation that would include a powerful new regulator to keep a much tighter grip on institutions considered “too big to fail.”

At the same time, Mr. Bernanke stoked a new controversy by endorsing more flexible accounting rules that would not force banks to book as many losses during an economic downturn as current rules require.

In so doing, the Fed chairman came closer than other top officials to supporting a policy known as “regulatory forbearance,” a phrase that became an epithet among policy makers after the savings and loan crisis of the early 1990s.

Although the Fed chairman did not use that phrase, he called for reducing the “pro-cyclical” aspects of current regulation  the tendency of accounting rules and capital requirements to aggravate both financial retrenchment during a slowdown and financial excesses during a boom.