The Obama administration agrees that more regulation is needed. A proposal unveiled recently by Treasury Secretary Timothy F. Geithner won plaudits for trying to make derivatives trading less freewheeling and more accountable  a plan that hinges in part on using clearinghouses for the trades.

Critics in both the financial world and Congress say relying on clearinghouses would be problematic. They also say Mr. Geithner’s plan contains a major loophole, because little disclosure would be required for more complicated derivatives, like the type of customized, credit-default swaps that helped bring down A.I.G. A.I.G. sold insurance related to mortgage securities, essentially making a big bet that those mortgages would not default.

Mr. Rosen and other bank lobbyists have pushed on Capitol Hill to keep so-called customized swaps from being traded more openly. These are contracts written for the specific needs of a customer, whose one-of-a-kind nature makes them very hard to value or trade. Mr. Rosen has also argued that dealers should be able to trade through venues closely affiliated with banks rather than through more independent platforms like exchanges.

Mr. Rosen’s confidential memo, dated Feb. 10 and obtained by The New York Times, recommended that the biggest participants in the derivatives market should continue to be overseen by the Federal Reserve Board. Critics say the Fed has been an overly friendly regulator, which is why big banks favor it.

Mr. Rosen’s proposal for change was similar to the Treasury Department’s recently announced plan to increase oversight. Treasury officials say that their proposal was arrived at independently and that they sought input from dozens of sources.

Even so, market participants, analysts and members of Congress who have proposed stricter reforms worry that the Treasury proposal does not go far enough to close several important regulatory gaps that allowed derivatives to play such a destructive role in the current financial crisis.

But increased transparency of derivatives trades would cut into banks’ profits  hence the banks’ opposition. Customers who trade derivatives would pay less if they knew what the prevailing market prices were.