Fed Chair Janet Yellen said Tuesday that banks are "very much stronger" and another financial crisis is unlikely anytime soon.

Speaking during an exchange in London with British Academy President Lord Nicholas Stern, the central bank chief said the Fed has learned lessons from the financial crisis and has brought stability to the banking system.

Banks last week passed the first round of the Fed's stress tests to see how they would perform under adverse conditions like a 10 percent unemployment rate and turbulence in commercial real estate and corporate debt.

"I think the public can see the capital positions of the major banks are very much stronger this year," Yellen said. "All of the firms passed the quantitative parts of the stress tests."

She also made a bold prediction: that another financial crisis the likes of the one that exploded in 2008 was not likely "in our lifetime." The crisis, which erupted in September 2008 with the implosion of Lehman Brothers but had been stewing for years, would have been "worse than the Great Depression" without the Fed's intervention, Yellen said.