A former Office of Management and Budget regulatory chief has come to the defense of a Washington institution: the expense-account lunch.

Jim J. Tozzi, who worked at OMB from 1972 to 1983, has written Donald E. Campbell, acting director of the Office of Government Ethics, to criticize the executive branch's tougher stance prohibiting lunches between reporters and their government sources.

It should be noted that Tozzi now works as a consultant on trade and regulatory issues in town, but he said that personal considerations aren't at issue in his protest.

"Federal managers are being increasingly harassed by unnecessary regulations," Tozzi said. "I am concerned that federal employes are being unfairly singled out on the question of business meals, based on an interpretation of a 22-year-old executive order."

To bolster his case, Tozzi sent along a five-page "memorandum of law" written by a lawyer colleague, Richard Berg, former general counsel of the Administrative Conference of the United States. Said Berg: "The chilling effects of the OGE {Ethics Office} ruling should be weighed against its dubious prophylactic advantages." Appointments at HHS and State . . .

Richard Williamson, a Chicago lawyer and White House aide from 1981 to 1983, has been named by the president to succeed Alan Keyes as assistant secretary of state for international organization affairs. Keyes resigned in a dispute with Deputy Secretary of State John C. Whitehead over U.S. contributions to the United Nations.

At the Department of Health and Human Services, Catherine Bertini has taken over the Office of Family Assistance. The office administers the Aid to Families With Dependent Children program. Hodel and the Korean War Memorial . . .

With Veterans Day obviously in mind, Interior Secretary Donald Hodel has signed letters to congressional leaders backing legislation to permit a Korean war memorial on or near the Mall. Congress has already approved a $1 million appropriation for the monument, with the rest expected to come from private contributions.

Meanwhile, the department's Bureau of Reclamation has hit a snag over its moving plans. The House Appropriations Committee voted to block a proposal to move bureau headquarters from Washington to Denver as part of a major reorientation of the water agency. Bureau officials want to get away from dam building and into water quality and environmental issues, but Rep. Tom Bevill (D-Ala.) says he needs more details. Candidates as Administrators . . .

The Center for Excellence in Government is running a campaign-year operation, the 1988 Presidential Candidate Series. The center, made up of about 300 business leaders who once were government executives, wants to find out how the candidates would govern, concentrating on "management style" and public service ideas. Democrat Bruce Babbitt kicked off the center's dialogue, staying firmly in the mainstream on at least one point: "In terms of administrative style, it seems to me that Carter and Reagan bracket the debate."