Sen. Arlen Specter (R-Pa.), a member of the Senate Select Committee on Intelligence, yesterday introduced legislative reforms for the Central Intelligence Agency stemming from the Iran-contra scandal, including a proposal calling for mandatory prison terms for government officials convicted of lying to Congress.

He also joined other Senate and House members who have proposed that President Reagan and his successors be required by law to inform Congress within one or two days after approval of any covert intelligence operations.

Specter also proposed splitting the director of central intelligence job into two posts: a director of national intelligence to be the president's primary adviser on foreign intelligence, supervise all U.S. intelligence-gathering agencies, and serve as a member of the National Security Council, and a director of the Central Intelligence Agency to manage the agency and carry out covert action.

Currently, the CIA director is charged with providing the president and his advisers objective intelligence relating to policy and at the same time carrying out covert operations to support that policy.

Specter said that splitting the job would end what he called problems of "objectivity and reliability" created by a "foreign policy activist" such as the late William J. Casey. Referring to differences that developed between CIA Director Casey and Secretary of State George P. Shultz, Specter said, "We cannot afford to have two secretaries of state, two foreign policy-makers who may be attempting to move the country in different directions, one overtly and the other covertly."

Casey, Specter said, was not the first director "who desired to be involved to some degree in the formulation or implementation of foreign policy, nor is he likely to be the last."

Specter called for a presidentially appointed, independent inspector general for the CIA. The CIA is one of the few government agencies whose director still appoints his own inspector general, which Specter said "is not conducive to objectivity."

He pointed out that the CIA official with operational responsibility for the controversial 1984 mining of Nicaraguan harbors was later named inspector general.

Other sources pointed out yesterday that the current inspector general's investigation of CIA activities on behalf of the Nicaraguan contra rebels during the time it was prohibited by law had to be redone when it became apparent that agency personnel were giving him false stories.

Specter's proposal for congressional notification of all covert actions within 24 hours after presidential approval appears to have the best chance for passage because versions of it have already been introduced by top members of the House and Senate intelligence panels.

Sen. William S. Cohen (R-Maine), vice chairman of the Senate committee, introduced legislation requiring notice within 48 hours. Cohen is expected to announce today that his measure is supported by intelligence committee Chairman Sen. David L. Boren (D-Okla.) and three key members of the Iran-contra investigating panel: Sen. Daniel K. Inouye (D-Hawaii), the chairman; Sen. Warren B. Rudman (R-N.H.), the vice chairman, and Sen. George J. Mitchell (D-Maine).

Under law, the president is required to consult with Congress in advance on covert operations, but the chief executive is allowed, in special circumstances, to give only "timely notice" after an operation has begun.

Reagan used that loophole to delay telling Congress about the Iran arms sales until after they were exposed in the press 10 months later.

The White House has traditionally opposed a time limit on such notification, and in a letter to Boren and Cohen after the Iran-contra hearings ended, Reagan indicated he still would demand the right to delay notification in special circumstances.

In demanding jail sentences for officials found deliberately misleading committees, Specter argued that congressional oversight cannot be accomplished if Congress is given false or misleading testimony. Specter said the situation is "especially problemsome where witnesses appear before the intelligence committees in a secret session . . . . Under those circumstances, the committees realistically have little or no opportunity to determine the truth."