Advance galleys of Mr. Bell's memoirs were mailed last week by the publisher to various news organizations, including The New York Times. Several news organzations, including some Washington radio and television stations, reported the controversial statements contained in the book in broadcasts today.

Marlin Fitzwater, the White House spokesman, told reporters today that he had not heard any such racial slurs, adding: ''And I think they would be wrong and, frankly, I don't believe it.''

Asked whether he thought Mr. Reagan participated in any such jokes or would have tolerated it, Mr. Fitzwater said no. ''I think it's beneath the dignity of the President,'' Mr. Fitzwater said.

But heads of some civil rights groups said they were ''not surprised'' by the assertions.

''I'm surprised to learn that it was a member of the President's inner circle that has finally revealed the kind of incidents many of us suspected were going on all along,'' said William S. Gibson, chairman of the Board of the National Association for the Advancement of Colored People. ''People tend to pick up the same kind of idiosyncrasies exhibited by their leaders.''

Vincent Reed, a former assistant Secretary of Education under Mr. Bell who is now a vice president of communications for the Washington Post Company, said he did not hear any such scurrilous remarks when he was in Government. ''But I didn't go the White House,'' Mr. Reed said.