The lawsuit filed in Manhattan bankruptcy court accused JPMorgan of using its "unparalleled access" to inside details of Lehman’s distress to extract $8.6 billion (£5.98bn) of collateral in the four business days ahead of Lehman’s 15 September, 2008, bankruptcy, including $5bn on the final business day.
JPMorgan was Lehman's main "clearing" bank, in which it acts as a go-between in Lehman's dealings with other parties.
According to the complaint, JPMorgan knew from this relationship that Lehman's viability was fast weakening, and threatened to deprive Lehman of critical clearing services unless it posted an excessive amount of collateral.
"With this financial gun to Lehman's head, JPMorgan was able to extract extraordinarily one-sided agreements from Lehman literally overnight," the complaint said. "Those billions of dollars in collateral rightfully belong to the Lehman estate and its creditors."
Lehman also said JPMorgan officials including Chief Executive Jamie Dimon decided to extract the collateral after learning from meetings with Federal Reserve Chairman Ben Bernanke and then-U.S. Treasury Secretary Henry Paulson that the government would not rescue Lehman from bankruptcy.
In the widely expected lawsuit, Lehman and its official committee of unsecured creditors are seeking $5bn of damages, a return of the collateral and other remedies.
JPMorgan spokesman Joe Evangelisti called the lawsuit "meritless," and said the bank will defend against it.