The three former chairmen of the U.S. Commission on Civil Rights yesterday issued a statement opposing President Reagan's firing of three commissioners because they said they are "alarmed by the administration's attempt to interfere with the independence and impartiality of the Commission on Civil Rights."

In addition to the former chairmen, six other former civil rights commissioners signed the statement opposing the president's actions. Only three former commissioners did not sign the statement. One of them, a publisher, said he refused on the principle that he should refrain from political activity and another, a judge, was not asked to sign because of his position.

"In its 25-year history the commission has not been the handmaiden of either political party," the statement said, and "this long tradition of independence has enabled commissioners to speak without fear or favor when criticizing shortcomings or praising progress in the field of civil rights.

"The actions of this administration, however, would overturn 25 years of tradition by removing five of the six commissioners Reagan earlier replaced the chairman and one commissioner ; subjecting the commission's reports and testimony to pre-clearance by the Office of Management and Budget and appointing as staff director a person rejected by the commissioners."

The three former chairmen are Dr. Arthur S. Flemming, now chairman of the Citizens Commission on Civil Rights; John Hannah of Michigan State University, and the Rev. Theodore M. Hesburgh, president of Notre Dame University.

The other six former commissioners who signed the statement were Frankie Freeman, Dr. Hector P. Garcia, Erwin N. Griswold, Dr. George M. Johnson, Maurice B. Mitchell, and Manuel Ruiz Jr.

The only former commissioner to decline signing the statement was Stephen Horn, president of California State University at Long Beach.

Eugene Patterson, publisher of the St. Petersburg Times, declined to take a position, and Judge Spottswood W. Robinson III, chief judge of the U.S. Circuit Court of Appeals for the District of Columbia, was not asked to sign because of his position.