The number of banks that had non-performing assets equal to at least 5 percent or more of their assets — considered a critical threshold - more than doubled in the year through June, according to data compiled by Bloomberg.

Altogether, the 150 banks hold assets of $193 billion, 15 times the FDIC's entire insurance fund.

“These numbers are off the charts,” says Blake Howells, an analyst at Becker Capital Management, referring to the nonperforming loan levels at companies he follows.

Banks are losing the “ability to try and earn their way through the cycle.”

The biggest banks with nonperforming loans of at least 5 percent include Wisconsin’s Marshall & Ilsley Corp. and Georgia’s Synovus Financial Corp., Bloomberg reports.

Among those exceeding 10 percent, the biggest in the 50 U.S. states is Michigan’s Flagstar Bancorp.

All the banks said in second quarter filings that they’re “well-capitalized” by regulatory standards, which means they’re considered financially sound.

A Congressional oversight panel’s latest report card on government rescue programs said significant problems will remain as long as bad bank loans create uncertainty about future losses, making banks less likely to lend and investors less likely to provide money to credit markets.

“The problem of troubled assets is especially serious for the balance sheets of small banks,” the report said, adding that these banks “hold greater concentrations of commercial real estate loans, which pose a potential threat of high defaults.”