Blackwater USA, the security company that has come under intense scrutiny on Capitol Hill after a September 16 incident in which it allegedly opened fire on Iraqi civilians and killed 17, was accused on Monday by a senior Democratic lawmaker of evading tens of millions of dollars in federal taxes.

Henry Waxman, chairman of the House oversight committee, who is leading congressional investigations into Blackwater, said that a newly discovered March 2007 ruling by the Internal Revenue Service, the tax authority, found that Blackwater’s designation of one of its employees as an “independent contractor” was “without merit”.