The United States sued Deutsche Bank AG for more than $1 billion, accusing the German bank of defrauding the government by repeatedly lying to obtain federal insurance guarantees on mortgage debt.

The lawsuit filed Tuesday against Deutsche Bank and its MortgageIT Inc unit is believed to be among the first targeting mortgage lenders under the federal False Claims Act.

It also marks the newest push by the government to hold the mortgage industry responsible for perceived excesses that contributed to a four-year-old U.S. housing slump and hundreds of thousands of foreclosures. It is unclear whether the government will target other banks in lawsuits.

Deutsche Bank shares fell 3.1 percent in late afternoon trading in Frankfurt.

“We just received the complaint and are reviewing it,” a Deutsche Bank spokeswoman said. “We believe the claims against MortgageIT and Deutsche Bank are unreasonable and unfair, and we intend to defend against the action vigorously.”

The complaint was filed in U.S. District Court in Manhattan. The government says MortgageIT from 1999 to 2009 endorsed more than 39,000 mortgages with principal totaling more than $5 billion for Federal Housing Administration insurance, meaning they were backed by the federal government.

Knowing they would profit from the eventual resale of the loans, the defendants were accused of recklessly choosing mortgages that violated program rules “in blatant disregard” of whether borrowers actually had the ability to make payments.

The government said it has paid out more than $386 million of FHA insurance claims and related costs, and expects to pay out hundreds of millions of dollars more.

“Deutsche Bank and MortgageIT had powerful financial incentives to invest resources into generating as many FHA-insured mortgages as quickly as possible for resale to investors,” the complaint said.

“By contrast, Deutsche Bank and MortgageIT had few financial incentives to invest resources into ensuring the quality of its FHA-insured mortgages.”

The complaint seeks triple damages on the $386 million of claims, as well as punitive damages, fines and other remedies.

Deutsche Bank bought MortgageIT for $430 million in 2007.

The office of U.S. Attorney Preet Bharara in Manhattan, which brought the case, had no immediate comment.

The bank was also a target of last month’s report by the U.S. Senate’s Permanent Subcommittee on Investigations criticizing lenders for contributing to the financial crisis.

That report detailed how investigators believed Deutsche Bank deceived clients into buying securities it believed were likely to implode.

Deutsche Bank lost an estimated $4.5 billion tied to the mortgage market collapse, but could have lost more had it not sold such securities, the report said.

The case is U.S. v. Deutsche Bank AG et al, U.S. District Court, Southern District of New York, No. 11-02976.