Max Brown, the ferociously loyal aide to Mayor Anthony A. Williams who was dubbed "the Enforcer" by some, said yesterday that he is leaving government for the private sector.

Brown, 35, who is deputy chief of staff and legal counsel to Williams (D), will join the Carmen Group Inc. lobbying firm as executive vice president and chief operating officer. His last day in the Williams administration will be Feb. 15.

"It was a very tough decision," said Brown, who spent three years working for Williams when he was chief financial officer. Brown and other staff members left the CFO's office to run Williams's successful mayoral campaign.

"I feel so much loyalty and affection for the mayor, and I've been part of a tremendous reform effort and will continue to assist the mayor and the administration from the outside," he said.

Williams said in a statement that he is "deeply saddened to see Max leave." Brown, he said, "has demonstrated hard work, excellence, commitment and dedication that has helped make the District government a more efficient and better functioning operation." The mayor has referred to Brown as his "right-hand man."

Brown's aggressive manner in promoting and protecting Williams's interests rubbed some community activists the wrong way. And some black activists, in particular, have criticized Brown, who is white, as disrespectful and as a symbol of Williams's lack of connection to the city's African American community.

The Carmen Group's clients include national and international companies, trade associations and foreign governments. The firm has 70 employees and annual revenue of nearly $10 million.

Brown and his wife, Katharine Mason, are expecting their first child in June. He said the Carmen Group presented him with "an opportunity I couldn't refuse." In addition to having day-to-day responsibility for four company divisions, Brown will work with David Carmen, the firm's chief executive officer, in developing a venture capital division that will specialize in technology start-up companies.

Carmen said in a statement, "We look forward to utilizing Max's management skills to achieve our mission of building Washington's most progressive and professional issue advocacy firm."

CAPTION: Max Brown's aggressive loyalty to the mayor has made him a controversial figure.