The chairmen of the House and Senate Banking Committees have warned Federal Reserve Board chairman G. William Miller against paying interest on member bank deposits at the Fed (so-called required reserves) without specific congressional approval.

Rep. Henry S. Reuss (D-Wis.) and Sen. William Proxmire told Miller in a letter that they are sympathetic to the Fed's concern about the large numbers of banks that leave the Federal Reserve system, preferring to be regulated by state banking authorities instead.

Most state regulatory authorities permit banks to earn income on required reserves.

A spokesman for the Fed said the central bank would have to comment on the Proxmire-Reuss letter until Miller replies formally.

Proxmire and Reuss sent the letter Monday and released it yesterday.

Miller in an earlier letter said that he believes the Fed has the authority to pay interest on member bank accounts, even though it has never done so in the past.

The Federal Reserve earns about $7 billion a year in interest on the hundreds of billions of government securities it owns as a result of the open market trading it does to control monetary policy.

The Fed uses that income to pay its expenses and returns the rest to the Federal Treasury. Last year the Fed earned $6.89 billion and returned $5.94 billion to the Treasury.

Proxmire and Reuss told Miller, "We are totally and unalterably opposed to any plan, proposal or draft regulation which purports to authorize the payment of interest on reserve balances without specific legislative approval from the Congress."

Miller said in a speech to the National Press Club Wednesday that he expects to have a plan ready by the end of the month designed to stem the flight of banks from the Federal Reserve system.

After World War II the Fed member banks accounted for 85 percent of all banking assets in the nation. Last year they accounted for 72 percent.

In the first six months of 1977 45 banks left the Federal Reserve system, compared with 46 in all of 1976. About 6,700 of the nation's 14,700 banks are members of the Fed system. All nationally chartered banks are required to be members and many state-chartered banks join by choice.

The Fed complains that when banks leave the system, the central bank's control over monetary policy is eroded.

The Treasury has offered a bill to Congress that would authorize the Fed to pay interest on member bank deposits, which Reuss and Proxmire say backs their argument that the Fed does not now have such authority without legislation.

The two Wisconsin Democrats said that if the Fed were to decide unilaterally to use its earnings to pay interest to member banks, it "could ultimately add billions of dollars to the federal deficit and could be viewed as a precedent for carte blanche authority for the expenditure of Federal Reserve bank earnings without restraint by either the executive or legislative branches of the government."

It could be the "opening wedge in a serious breach of the constitutional power of the Congress and the president to control federal spending and determine the fiscal policy of the nattion," they said.