The American Federation of Government Employees, the largest federal workers' union, announced the start of a national "image campaign" yesterday to improve the public's appreciation of federal employes.

Starting in nine targeted cities -- including Washington and Baltimore -- with a $300,000 preliminary advertising budget, the union will kick off the campaign with radio ads emphasizing the broad range of vital services provided by more than 2 million federal workers.

Citing "attacks" by the Reagan administration on the quality and competency of federal workers, AFGE President Kenneth T. Blaylock said the campaign would attempt to educate the public about the importance of federal government services.

"We want to put the politics and the stereotypes aside and show the diversity and dedication of federal workers -- the people who inspect the food we eat, get the Social Security checks out, keep the borders safe, and the list can go on and on," Blaylock said.

The campaign is the first such effort undertaken by the 225,000-member AFL-CIO-affiliated union, which has been among the groups opposing the administration's proposed pay and benefit cuts for federal employes. The union represents employes at 67 federal agencies employing 750,000 federal workers.

"Dedicated Americans Keeping Our Country Strong" is the theme of the radio ads that begin this week in the target cities and on 1,300 stations served by CBS and Mutual radio networks. The other cities are Atlanta, Boston, St. Louis, San Francisco, Seattle, San Antonio and Oklahoma City.

Donald J. Devine, director of the Office of Personnel Management, said yesterday the AFGE effort is "great. We should promote the image of federal employes any time we can. But it is important to promote the fact that we have to make some changes for federal employes too . . . . The only way we are going to improve the image of federal employes is to make the government work better and reduce its size and intrusiveness into people's daily lives."

Following the initial radio ads, the campaign will also include regional radio and newspaper ads, posters, fliers and other materials emphasizing local services and issues. The union has created a media fund to collect contributions from members and supporters to continue the campaign following the initial phase.