Welcome to the brave new world of central banking at the Federal Reserve: more powerful, but messier and prone to entanglements that could threaten its ­independence.

The Fed has always had bank supervision responsibilities and Ben Bernanke, its chairman, argues this makes it more effective than those that conduct only monetary policy. But the reforms elevate and formalise the US central bank’s role as the nation’s financial stability agency, giving it new powers and responsibilities oriented against systemic risk.