The U.S. government has joined a whistleblower lawsuit that alleges defense contractor Lockheed Martin Corp., vendor Tools & Metals Inc. and former executives of TMI overcharged the government by millions of dollars, the U.S. Department of Justice said Monday.

The lawsuit filed by a former TMI account executive and a TMI competitor alleges that former TMI President and Chief Executive Todd Loftis overcharged for manufacturing tools sold to Lockheed Martin, which resulted in Lockheed Martin submitting false claims to the Defense Department from January 1998 through February 2006.