Sen. James B. Allen (D-Ala.) yesterday blocked a resolution that would have permitted subpenaed information relating to franked mass mailings by individual senators to be turned over to a federal district court here.

Cornelius B. Kennedy, a lawyer for subpenaed Senate employees and the Senate itself, on Monday surprised his clients by agreeing to turn the material over to a three-judge panel.

The judges are hearing a lawsuit brought four years ago by Common Cause and aimed at ending the franking privilege for members of Congress. Lawyers in the case had thought contempt citations might be ordered before Kennedy made his unexpected offer to provide the material. Some of which had been subpanaed more than two years ago.

Allen said yesterday Kennedy "had been given certain instructions" before Monday's court hearing, "and now is departing from them."

Prior to Monday's court session, Kennedy was given a memorandum by the Senate's Ad Hoe Committee on Legislative Immunity which has monitored the four-year-old lawsuit.

The memo termed the information demanded by Common Cause's subpoena "excessive" and said "the Senate cannot accede to . . . demands of this kind."

When the court convened, however, Kennedy agreed to supply the information for examination by the judges to see if it is relevant to the lawsuit.

Judge Malcolm R. Wilkey gave Kennedy two weeks tp produce the initial part of the information sought.

Under Senate rules, Kennedy needed a resolution of the Senate authorizing his delivery of the information.

Sen. Lee Metcalf (D-Mont.), chairman of the legislative immunity committee, tried to get such a resolution passed by unanimous consent yesterday.

When Allen objected, Metcalf said that "Kennedy had made a commitment to the court" but that "it wasn't a commitment agred to by the Democratic conference or any member of the ad hoc committee."

Allen instead got approval to have the matter studied by the Rules Committee.