WASHINGTON (Reuters) - The U.S. Senate approved William Lynn, a former Raytheon Co lobbyist, to be deputy secretary of defense after he received a special White House waiver from strict new rules meant to close a “revolving door” between government and big business.

Lynn, the Pentagon’s chief financial officer from November 1997 to January 2001 under former President Bill Clinton, was confirmed by a vote of 93 to 4 on Wednesday.

At Raytheon, the world’s biggest missile-maker and the Pentagon’s No. 6 supplier by sales, he was registered as the company’s top lobbyist to the Defense Department from July 2002 until last year.

President Barack Obama’s new ethics rules bar lobbyists for two years from working as appointees on matters they had lobbied about. The White House Office of Management and Budget gave Lynn a waiver to further “the public interest.”

Sen. Charles Grassley, an Iowa Republican noted for holding federal officials to account, deplored Lynn’s nomination in a floor speech before the vote.

“I think the Office of Government Ethics will have to set up a full-time department just to handle Mr. Lynn’s conflicts-of-interest Raytheon waivers,” said Grassley, who voted against confirmation.

Lynn has said he will steer clear for a year of decisions involving six big arms programs on which he lobbied on behalf of Raytheon.

They are the DDG-1000 multi-mission combat ship, Advanced Medium-Range Air-to-Air missile, F-15 airborne radar, Patriot missile “Pure Fleet” modernization, the National Reconnaissance Office’s Future Imagery Architecture, and the Missile Defense Agency’s Multiple Kill Vehicle.