Prince George's County Executive Lawrence J. Hogan, in an apparent effort to head off speculation about several of his major appointments yesterday issued a statement naming County Council administrator Kenneth V. Duncan as the county's chief administrative officer.

Hogan also said he would name his son, Lawrence J. Hogan Jr., as one of his staff aides.

At a hastily called press conference late yeaterday afternoon, Hogan aides distributed a list of 10 appointments, a list including the name of former Republican councilman John B. Burchma Jr., who will be chairman of the planning board.

Lawrence Hagan Jr., according to the statement, will act as his father's "personal representative to the governor's office and mayor's as well as representing his father at ceremonial functions."

Although senior aides to the county executive earn between $24,000 and $32,000 annually, Hogan press aide Barbara Coleman said Hogan hopes to amend the employe classificaton plan to give his son a salary of $11,000.

Both Hogan and his son had left the executive office before the press conference yesterday afternoon and were unavailable for comment.

Hogan also said he has asked Marion H. Estepp to stay on as the county's fire chief. However, Hogan has already announced that he will appoint a county safety director to whom both the police and fire chiefs will report.

The appointments of both Duncan and Burcham will require approval by the County Council but council members have already reviewed and given preliminary approval to the nominations, Coleman siad. No council approval is required for Lawrence Hogan Jr.'s job since it is an executive's staff position, but Hogan's planned amendment allowing him to lower the salary for the job will require council approval.

Duncan, who had already been named by several council members as Hogan's selection for the administrative officer's position, has been council administrator since 1971 and is considered an expert on the county budget and on water and sewer matters, two areas where Hogan is faced with immediate decisions.

"He's a professional in whom the council has a great deal of confidence," said Councilman Panis N. Glendening. "He's going to have to be Hogan's man now. But he will be a source in the executive branch that we can have a great deal of confidence in - particulary when we get into the budget, where we are bound to have conflicts."

According to Glendening, Hogan has told council members that he hopes to send Duncan's appointment to the council early next week. But because the council must hold public hearings before confirming the appointment, Duncan will probably not take office until at least the second week of January, Glendening said.

Duncan will replace Robert W. Wilson, who has accepted the job of chief administrative officer in Montgomery County.

Burcham, if approved by the council, will replace W. C. Dutton as the chairman of the County Planning Board, which forms part of the bicounty park and planning commission.

Burcham, who ran unsuccessfully for the County Council this fall, has not worked with the planning board since he was a councilman between 1970-74, and said he plans to retain his current position as excutive director of the National Liquor Stores Association.

Burcham said that Hogan, who has said that he would like the Maryland legislature to split up the park and planning commission into two agencies run by the "governments of each county," said he will make the positions of planning board chairman and park and planning commissioners part-time in the future.