Top Democrats on the Senate and House natural resources committees urged the Interior Department on Tuesday to drop a proposed cut to offshore oil and gas royalties, warning such a reduction would shortchange U.S. taxpayers.  The Interior Department’s Royalty Policy Committee is due to evaluate a proposal to lower the royalty rate companies pay on petroleum produced in federal offshore waters to 12.5 percent from 18.75 percent – part of a plan by the Trump administration to encourage more U.S. energy production.  “This proposal would amount to a giveaway to some of the most profitable companies in the world and rob taxpayers of potentially billions of dollars of revenues over the life of the leases,” Senator Maria Cantwell of Washington and Representative Raul Grijalva of Arizona wrote to Interior Secretary Ryan Zinke.  They said in the letter that the royalty committee appointed by Zinke – made up of members from the Interior Department, states, tribes and oil, gas and coal companies – was “stacked with resources extraction interests.”