NEW YORK – The bank used most by Bernard Madoff was “willfully blind” and “thoroughly complicit” in the disgraced financier’s epic fraud, lawyers working for a court-appointed trustee alleged Thursday.

JP Morgan Chase responded by accusing trustee Irving Picard of “blatantly distorting” the bank’s role.

Picard is in the midst of a nearly two-year quest to recover funds for Madoff’s victims with a flurry of lawsuits against financial institutions and brokers. The latest suit, filed in federal bankruptcy court in Manhattan, seeks $6.4 billion from JP Morgan and its affiliates.

The suit alleges that as Madoff’s primary bank for 20 years, JP Morgan had to know that the unwavering double-digit returns Madoff reported to wealthy investors were too good to be true. The trustee cited bank documents showing questionable transactions by Madoff as evidence it was in on the scheme.

The bank “was willfully blind to the fraud, even after learning about numerous red flags surrounding Madoff,” said David J. Sheehan, an attorney working for Picard.

“While many financial institutions enabled Madoff’s fraud, JPMC was at the very center of that fraud, and thoroughly complicit in it. Madoff would not have been able to commit this massive Ponzi scheme without this bank.”

In a statement, JP Morgan denied having any suspicions about Madoff. It said it followed all commercial banking regulations in its dealings with him.

“The complaint filed today by the trustee for the Madoff estate blatantly distorts both the facts and the law in an attempt to grab headlines,” the statement said. “Any suggestion that JP Morgan supported Madoff’s fraud is utterly baseless and demonstrably false.”

The trustee seeks $5.4 billion in damages and $1 billion in fees and profits.