Clement Conger, curator of the White House since 1969, has been asked to leave his post so he can be replaced by former White House chief usher Rex Scouten, informed sources said yesterday.

"It would be inaccurate to say the first lady fired Conger," said Chris Hicks, deputy assistant to the president for administration. "I checked with Don Regan and he said that's absolutely wrong."

An official who would not be named said First Lady Nancy Reagan had asked Conger to leave in favor of Scouten, who is thought to be a Reagan favorite. The first lady in January named her King Charles spaniel after him. Scouten was chief usher, or manager, of the White House from 1969 to January 1986. Some have said he was already bored with retirement and wanted to come back to the White House. Conger, from the beginning, has usually spent only half his time at the White House.

Hicks said Conger was "withdrawing" from the White House to devote all his attention to the State Department Diplomatic Reception Rooms, and to the $12.6 million restoration and redecoration of Blair House. Scouten's appointment has not been announced and Hicks said no replacement has been officially named.

Conger, reached at a meeting in Wilmington, Del., of the White House Preservation Fund, said he would have no official statement at this time.

Conger for some time has told friends he would like to leave the White House job if a professional, trained decorative arts curator could be appointed to the job. He and Scouten, who is not a professional curator, have not always seen eye to eye on maintaining and decorating the White House.

Conger has also voiced disappointment with Nancy Reagan's lack of support for the White House Preservation Fund, set up to raise $25 million for the First Mansion. The first lady is said to have been deterred from such sponsorship by the furor over her redecoration of the family quarters early in her husband's first administration. The Reagans are also the first White House family, since the law was passed in the Johnson administration, not to name a committee for the preservation of the White House, a group set up to oversee changes in the historical rooms.

Conger has been curator since the Richard Nixon presidency, when he raised $15 million to redecorate the State Rooms in the style of the early 19th century. His redecoration, under the supervision of the late Edward Vason Jones, an authority on the Federal period, obliterated the earlier efforts of Jacqueline Kennedy.

Conger retains his jobs as curator of the State Department Diplomatic Reception Rooms, chairman of State's Fine Arts Committee and curator of Blair House.

Conger, 73, has just finished raising $3.5 million to remodel the State Department Benjamin Franklin great hall and $2.25 million to redo Secretary of State George Shultz's office. In the 25-year history of the renovations at the State Department, he has raised $10 million for architectural renovations and $30 million in Federal antique furniture and decorative objects.

Conger is said to have raised more money for the United States government than any one outside the Internal Revenue Service. His salary, all paid out of the State Department budget, is about $65,000. Honorariums for his speeches go into the decoration funds.

First indications of trouble between Conger and the first lady came early in the first Reagan term when Mrs. Reagan brought in California decorator Ted Graber to redecorate the family quarters on the White House's second floor. Conger once said, "They didn't feel any need to consult me on the upstairs, though they did use the antiques I collected."